Abstract: In order to improve the efficiency of t-test in the leakage detection of Block Cipher power information, a new t-test method was proposed.Firstly, the basic steps of t-test to detect power information leakage were introduced.The nonlinear property of S-box was studied by Walsh spectrum.The concept of transparent order was introduced and its relation with nonlinearity was deduced.And the relationship between the nonlinearity of the output bits of the S-box and the leakage of power information was further established.And then, a method was proposed to determine the order of performing t-test on the output bits of the S-box, so as to the sequential detection carried out according to the nonlinearity of the output bits of the S-box.Finally, the first round S-box of DES encryption algorithm was used as an example for verification.The results show that the proposed method can effectively improve the detection efficiency of power information leakage by t-test.