In August 2010, Chinese laser team succeeded in improving the performance of the petawatt (PW) femtosecond Ti:sapphire chirped pulse amplification (CPA) laser system at Shanghai Institute of Optics and Fine Mechanics (SIOM). By enlarging the sizes of the pump and signal beams in the large aperture Ti:sapphire amplifiers and optimizing the whole laser system, the output laser energy before the pulse compressor is upgraded to 42.6 J. Accordingly, the peak power of the laser system exceeds 1 PW from the original 0.89PW. The shot-to-shot instability of the output laser energy at about 40 J is less than ±5%. The PW femtosecond Ti:sapphire laser system has been used in high energy particle generation and acceleration successfully.