The mid-infrared spectral region of 2-20 µm, containing the molecular fingerprint region and atmospheric window, is considered one of the most promising spectral regions in the area of spectroscopic research. Mid-infrared dual-comb spectroscopy has significantly broadened the practical application domains of optical frequency combs and emerged as a powerful tool for the detection of greenhouse gases and the analysis of trace gas owing to its high signal-to-noise ratio, high resolution, high acquisition speed, and wide spectral bandwidth. While Mid-infrared dual-comb systems based on electro-optic combs or micro-resonators combs offer simple experimental setups, they have limited spectral bandwidth and number of comb teeth. The mid-infrared systems based on mode-locked lasers have significant advantages over frequency precision and resolution but require expensive servo systems to stabilize the repetition rate and carrier envelope offset rate. The two combs output by a single-cavity dual-wavelength laser have good relative frequency stability without complex phase-locking systems. Therefore, mid-infrared dual-comb systems based on single-cavity dual-wavelength lasers have excellent characteristics including low cost, simple structure, high integration, and high coherence. However, a problem of great importance that needs addressing is the slow drift of repetition rate difference in free-running single-cavity dual-wavelength systems. Furthermore, there is still room for further optimization of the integration of mid-infrared dual-comb sources.An all-polarization-maintaining single-cavity dual-wavelength erbium-doped fiber laser is built as the near-infrared light source, mode locked by semiconductor saturable absorber mirrors. The repetition rate difference (Δf_r) of two pulses output by the near-infrared fiber laser is precisely stabilized by a phase-locking system (Fig.1). The detection of multi-heterodyne beat notes is performed to demonstrate the coherence between two pulses (Fig.4). The supercontinuum in Si₃N₄ waveguide is seeded by pulses after amplification. The two combs multiplex a single silicon nitride waveguide to optimize the integration of mid-infrared system (Fig.1).The two pulses output by the single-cavity dual-wavelength erbium-doped fiber laser achieved highly overlapped spectrums with center wavelengths at 1560 nm and 1561 nm, and 3 dB spectral widths of 4.74 and 4.83 nm, respectively (Fig.2). The spectral widths of two pulses after amplification exhibited a significant increase, spanning from 1520 nm to 1580 nm, while maintaining a high degree of spectral overlap (Fig.2). Both pulses are amplified with an erbium-doped fiber amplifier so that they provide femto-second and high-intensity laser pulses (duration <100 fs, peak power >15 kW) to seed supercontinuum generation in Si₃N₄ waveguide (Fig.2). The near-infrared system demonstrated the capability to adjust Δf_r across a wide frequency range, spanning from 0 to 41.9 kHz (Fig.2). Furthermore, the frequency jitter of Δf_r was reduced from Hz to MHz order of magnitude using the phase-locking system (Fig.3). The radio frequency domain multi-heterodyne beat notes exhibited clear comb teeth, indicating high coherence between two combs (Fig.4). The broadband mid-infrared spectrums based on supercontinuum generation in the silicon nitride waveguide were successfully accomplished, covering the important spectral range of 3.2-3.6 µm (Fig.5).The experimental results demonstrated the generation of a highly integrated and coherent mid-infrared dual-comb source based on supercontinuum generation in the silicon nitride waveguide seeded by a single-cavity dual-wavelength erbium-doped fiber laser. The frequency jitter of Δf_r was effectively stabilized by a phase-locking system, resulting in a highly coherent dual-comb source with standard deviation of frequency jitter of Δf_r reduced to the sub-mHz order of magnitude. The peak powers of both pulses after amplification were 15 and 17 kW, respectively. The high-intensity pulses multiplexed the same silicon nitride waveguide for supercontinuum generation, generating highly overlapping mid-infrared spectrums with spectrum widths of 2 µm and significantly improving the integration of the mid-infrared system. The broadband mid-infrared spectrums both cover the important spectral range of 3.2-3.6 µm, which is applicable to the detection of hydrocarbon molecules. The integrated mid-infrared system combines the advantages of high integration, high coherence, and broad bandwidth, providing a reliable light source for subsequent mid-infrared dual-comb spectroscopy applications.