The photocurrent is very small when the visible light irradiates the semi-insulating silicon carbide. The femtosecond laser pulses are used to modify the silicon carbide surface, and the result shows that the photocurrent is enlarged several times according to the measurement results of photoconductivity. In order to explain the reasons for this change, some characterization means are employed, including the absorption, emission and X-ray photoelectron spectra. There are found some changes in the absorption spectra and emission spectra, and also in the silicon and carbon atom ratio according to the test results of X-ray photoelectron spectrum. We think that the changes of the crystal structure and atom ratio between silicon and carbon lead to the change of electronic energy band structure and the occurrence of many defect states. As a result, the photocurrents are improved in the range of visible light on the surface of 6H-SiC after the femtosecond laser pulses have irradiated the surface.