The influence of spatial chirp on broadband ultrashort pulse laser system is analyzed. An experimental method for studying spatial chirp in SG-II-5 PW setup with wavefront sensor is proposed. In experiments, the wavefront feature of broadband ultrashort pulse laser is collected after the pulse passing through the stretcher and multi-stage spatial filters, and the lateral spatial chirp and the offset of the wavefront aberration centre relative to the optical axis of the system are measured. The dispersion regulator is adjusted in real-time to eliminate the spatial chirp in the laser system. The wavefront distributions before and after the spatial chirp elimination are compared, and the theoretical simulation shows that the focusing performance and the far field energy concentration of laser from SG-II-5 PW system are improved obviously.