By means of the method of SPIDER (Spectral Phase Interferometry for Direct Electrical Reconstruction) , the characteristics of the output of a 15 TW/35 fs table top Ti∶sapphire ultrashort ultraintense laser system have been measured, which include the phase and the time depended intensity of the pulse. The results show that the output pulse of this system has good relative phase distribution )the phase difference between every two spectrums<2π), and the duration of the output pulse is 33fs. Consequently, the system has reached the aim of the design.