In this paper,a model with two mutual learning neural networks named Tree Parity Machine(TPM) is firstly introduced,as well as its cryptographic property of weight synchronization with that of chaos cryptography is comparatively discussed. A full empirical study on the stability and security of the TPM weight synchronization is conducted in detail. Then two improvement methods for the weight synchronization are proposed. Experiment results show that the improved TPM synchronization model can be efficiently ...