There exists high density of electoonic surface states at the surface between GaAS material and air,by which the electrons of interior GaAs semiconductor material can relax with the relaxation time of picosecond level.By such principle,a new type of surface-state semiconductor saturable absorption mirror was introduced,with which we realize passive continuous wave modelocking of diode-end-pumped Nd:YAG laser.At the 4 W of pumping power,we obtain continuous wave modelocking series.which has 300 mW average output,150 MHz frequency and 1 ps pulse duration.