The invention belongs to the field of information security, and discloses a CRT-RSA selected plaintext joint attack method and system. During the attack process, the d p and d q As the attack target, then derive the private key parameters p, q; in the plaintext collision attack process, select multiple sets of plaintext pairs, superimpose them, and do secondary processing on the power consumption difference of the model multiplication as a collision classification set; in the attack process, Combined with the disclosure of the Hamming weight information of the access number power consumption exponent during the CRT-RSA modular exponentiation operation, the modular multiplication power consumption is segmented, and the segmented plaintext collision attack is implemented. The present invention combines the problems of other information leaks (such as access number power consumption exponent Hamming weight information leak) in the CRT-RSA modular exponentiation process, performs modular multiplication power consumption segmentation, and implements segmentation selection plaintext collision attacks, which can avoid partial The collision attack is wrong, thereby improving the attack accuracy, and finally deriving the private key parameters p, q, and recovering the private key d value.