In order to improve focal spot concentration of 3ω laser, entire beam wavefront should be corrected. One of key technologies is to get entire beam wavefront aberration exactly. With Hartman wavefront sensor located at parameters diagnosis unit of main amplifier, wavefront of output main amplifier can be obtained. However, wavefront of target system can′t be measured directly. There are two methods to solve this problem including reverse calibration and direct measurement at target point. By comparing complexity and accuracy of the two methods, and combining far field measurement with and without correction, direct measurement at target point is a simple and correct method to get entire beam wavefront.