Surface texturing is an effective method to reduce surface reflectance and improve the efficiency of silicon solar cell. In this paper, the black silicon antireflection coating is fabricated by using plasma immersion ion implantation. The surface morphology and reflectance are investigated by atomic force microscope and UV-VIS-NIR spectrophotometer, respectively. Results show that mountain-like structure with a depth of 0550 nm is fabricated on black silicon surface. Both the fractional area occupied by silicon and refractive index decrease smoothly with the increase of depth across the antireflection coating. The weighted average reflectance of black silicon is as low as 6.0% in a wavelength range of 3001000 nm. The depression mechanism of the optical reflectance is analyzed by simulating the structure with the transfer matrix method, and the simulation result fits the measured spectrum well.