Fe4N has been confirmed to possess high spin polarization of 81.3% and low Gilbert damping constant of 0.021 +/- 0.02 in the recent experiment To explore the potential applications of Fe4N in spintronics devices, the current-perpendicular-to-plane spin valve employing Fe4N as electrode and Ag as spacer is simulated to study the spin polarized quantum transport by utilizing the first principles calculations combined with nonequilibrium Green's function. The project density of states (PDOS), transmission coefficient, spin-polarized current, magnetoresistance (MR) ratio and spin injection efficiency (SW) as a function of bias voltage are studied. Our calculations reveal that spin down electron is the majority spin polarized electron and the absolute value of MR ratio of Fe4N/Ag/Fe4N at equilibrium reaches up to 174%, and it decreases with the bias increases. Besides, our results indicate that Fe4N/Ag/Fe4N device has stable SIE value of about 40% and stable MR ratios of about 150% when bias increases from 0 V to 0.1 V, and the device has a better performance within this voltage range.