A continuous-wave (CW) tunable NdYVO4-PPLN intra-cavity resonance single oscillator (ICSRO) under 880 nm laser diode (LD) resonance pumping is reported. 1.54 W maximum idler output power at 3.66 μm is obtained under the pump power of 21.9 W, corresponding to an optical-optical conversion efficiency of 7.0%. The ICSRO under 880 nm in-band pumping shows significant improvements in threshold, output power, conversion efficiency and power stability compared with that under 808 nm traditional pumping. Since the back-conversion process harms the single resonance oscillator (SRO) down-conversion efficiency under high pump power, the influence of output coupler transmittance on SRO threshold and down-conversion efficiency is investigated. By increasing the output coupling of resonant signal to raise the SRO threshold, the down-conversion efficiency can be maintained under high pump power and efficient signal output can be obtained. 1.54 W idler output and 5.03 W signal output are obtained under the pump power of 21.4 W, corresponding to a total extraction efficiency of 30.2%.