Abstract: We investigated responsivity of photodiodes fabricated with silicon that was microstructured by femtosecond-laser pulses in a sulfur-containing atmosphere. In different temperature annealing, the aluminum electrodes were prepared using the electron evaporation method according to different spike height of microstructured silicon. The femtosecond laser microstructured photodiodes were made, and the opto-electronic responsivities of photodiodes was measured. Test results show that the responsivity of photodiodes depends on the height of spikes and annealing temperature, the responsivity can be as high as 0.55 A/W. For wavelengths of 1100 nm below the bandgap we obtained responsivities about 0.4 A/W, which is higher than that for standard silicon photodiodes.