In dense wavelength division multiplexing systems, the light sources are difficult to be synchronized and costly. A structure of multi-carrier light source with good flatness, large number of subcarriers, large spectrum width and adjustable frequency spacing was proposed which can be used in dense wavelength division multiplexing systems. The structure is cascaded with a Mach-Zehnder modulator , an electro-absorption modulator and a phase modulator . In the structure, all the modulators can be driven by a sinusoidal signal to obtain multiple sub-carriers with low flatness and adjustable frequency spacing. When the driving signal frequency is 9 GHz and 12.5 GHz, the number of subcarriers is 31, the flatness of the generated multi-carrier light source can reach 0.09 dB. When the driving signal frequency is turned from 3 GHz to 16 GHz, the number of generated subcarriers is almost unchanged, and the flatness of the subcarriers is always less than 0.15 dB under the condition of 31 subcarriers. And when the driving signal frequency is 16 GHz, the spectrum width of the obtained multi-carrier light source can reach 480 GHz. In addition, the influence of the parameters, such as the upper and lower arm bias voltages of Mach-Zehnder modulator, the chirp factor and the modulation index of electro-absorption modulator, are analyzed with the performance of the system, such as the number of subcarriers, the spectrum width of the generated multi-carrier light source.