Abstract: The temperature of hot electron generated from the solid target irradiated by ultrashort pulse laser has been studied experimentally. The method is to measure the hard X-ray continuum generated by the high energy electron bremsstrahlung process in solid region. When moderate intensity, pre-pulse free, P-polarized light irradiates 5 mm Cu slab with 45°, the hard X-ray with energy up to 400 keV is detected. Fitting the experiment data by Maxwellian distribution, the temperature of hot electron is 85 keV, the main absorption mechanism for high energy electron generation is "vacuum heating".