KEELOQ rolling code technology with high security has been widely used in the automotive field. According to the rationale of Keeloq algorithm and the lack of its security, we provide a kind of Keeloq algorithm modification scheme to improve its security ,which can be applied in Passive Entry Passive Start(PEPS).The proposed scheme introduces a mechanism under the safe learning mode, in which the temporary key and seed code of each round can be generated by the key agreement process between the key terminal and the car terminal.Then, both value can be used for the key derived scheme.According to the security analysis and the performance comparison with the original Keeloq and triple Keeloq algorithm, we get the conclusion that,the improved scheme improves the security of the original algorithm without increasing the implementation complexity of the algorithm,and it is suited for PEPS.