A new kind of crystal, the O-axis Nd:YLF, is used to obtain the active, passive and active-passive mode-loking. The C-axis Nd:YLF emits at 1.053#m without inserting any polarizing elements in the cavity. The fluctuation of the emergy in a pulse train of the active-passive mode-looked laser is less than ±4%. The fluctuation of the pulse width is no more than ±10%.