A compact passively mode-locked laser with 7.5-m cavity length is reported. The laser is 55 cm in length and 15 cm in width by the resonator folding design. The Nd:YVO4 crystal is end-pumped by the diode laser. The output laser with double-pass of the gain crystal after passively mode locked by semiconductor saturable absorber is obtained. The repetition rate is 20 MHz and the pulse width is 14.2 ps, the average power is 6.14 W and the output laser is TEM00 at 1064 nm. The pulse energy is 0.3 μJ. The quality of laser beam M2 is 1.17 in X direction and 1.06 in Y direction. The power unstability is 0.5%.