An all normal-dispersion Yb-doped mode-locked fiber laser and its amplifier are demonstrated. The experiment system consists of two parts: nonlinear polarization rotation mode-locked fiber laser and amplifier with forward pump. In this experiment, a mode-locked fiber laser, whose repetition rate is 88.3 MHz, with the maximum average output power of 125 mW and 4 ps pulse width is obtained. After amplified, the maximum output power reaches 3.5 W on average, the pulse width and single pulse energy are 7.2 ps and39.64 nJ respectively.