A broadband erbium-doped passively mode-locked fiber laser is proposed and demonstrated. It lays the foundation for optical frequency comb and generation of fiber femtosecond pulse. Based on the mode-locked mechanism of nonlinear polarization rotation, the laser combines C-band and L-band erbium-doped fiber reasonably in large normal dispersion region to ensure that the laser has a gain spectrum coverage of C+L band. When the pump power reaches 350 mW, the pulses operate stably with fundamental frequency of 4.32 MHz, 3 dB bandwidth is 60 nm and 20 dB spectrum covers from 1522 nm to 1630 nm. The full coverage of gain bandwidth is achieved. The method can effectively avoid nonlinear phase noise of spectrum components by using gain splicing to broaden spectrum, and it is conducive to further compress pulse.