To gurantee the safety of mobile payment, this paper conducts a study on the security of the mobile e-commerce payment system based on WAP. It introduces the concept of information hiding and digital watermarking, and puts forward an anti-GSM voice compression coding algorithm based on ERA(Energy Ratio Adjustment). Moreover, the audio digital watermark is added to the system which has greatly strengthened the security of the WAP- based mobile e-commerce payment system.