Some chaotic sequences generated from maps conjugated with tent map can be reconstructed precisely by short sequence prediction,since the problem of finite precision degrades the statistical properties of chaotic maps.This paper discusses the topological conjugation properties of the chaotic maps;analyzes in detail the reconstruction process of the chaotic sequences and the security of the oversampled chaotic map (OSCM) binary sequences.The result demonstrates that OSCM binary sequences can sustain the attack of the short sequence prediction,that is,they cant be reconstructed.Furthermore,all attack strategies aiming at the chaotic systems based on synchronization will fail,meaning that they are secure.