In view of the demand of antireflection performance of titanium alloy optical device surface in aerospace field,the antireflection micro nano structure of TC4 titanium alloy surface is prepared by femtosecond pulsed laser in this experiment.Firstly,the effects of laser monopulse energy density and the number of pulse subpulses on the surface reflectivity and micromorphology of TC4 titanium alloy are investigated by means of 0°and 90° cross scanning of the sample by pulsed laser direct writing method,so as to avoid the surface hardness of titanium alloy from changing due to the thermal effect of processing,and to treat the samples by means of different modalities.The reflectance of TC4 titanium alloy samples is measured by spectrophotometer,and the microstructure of the samples is observed by scanning electron microscope (SEM).The results show that when the energy density of the laser is 1.27 J/cm2,the scanning speed is 300mm/s,the scanning distance is 0.0015mm,and the number of pulses subpulses is 1,the average reflectance of the sample reaches less than 1.70% in the visible wavelength band (400 nm～780 nm),and the reflectance reaches less than 1.30% at the wavelength of 300 nm.The results of this experiment can provide some guidance for the suppression of stray light on the surface of important devices such as the shutter and the position marker of satellite camera.