A passively mode-locked fiber ring laser with a small segment of Er3+-doped fiber as gain medium, pumped by a stable 980 nm laser diode and mode-locked by the nonlinear polarization rotation (NPR) technique, was successfully achieved. When the laser was pumped at 650 mW, stable mode-locked pulses centered at 1560 nm with 163 fs pulse width. The repetition rate is 31.25 MHz. The laser presented here has advantages of being easy to operate and adjust, long-running and better stability. The fiber structure is of miniaturization, integration and portability.