The formation of laser-induced surface microstructure on silicon under irradiation with femtosecond laser pulses scanning (pulse width 42 fs, center wavelength λ=800 nm, the maximum single pulse energy 3.6 mJ) at different temperatures is described. Scanning electron microscopy (SEM) and optical microscopy are used for observing the morphologies of the surface microstructure on silicon. It is found that the area and the morphologies of the microstructure on silicon both become different. According to the observations, the energy thresholds of producing microstructure on silicon at different temperatures are analyzed and compared. The damaged area of the silicon is reduced while the temperature rising. It is shown that the energy threshold of femtosecond laser ablation silicon surface to produce microstructure increases with the temperature rising. This is valuable for the study on femtosecond laser interaction with matter, and also for the formation of surface microstructure on silicon in the future.