Remote attestation is a focus research in Trusted Computing. There are some attestation approaches suggested such as configuration based or property based attestation, but these suggestions have a few fatal deficiencies to overcome, e.g., leakage of platform configuration privacy or hard to define trustworthiness related properties, etc.. To solve these problems, this paper presents a system behavior based attestation model which try to determine the trust state of attesting platform from its system trustworthiness related behaviors. The new attestation model has advantages of privacy protection and high feasibility. In addition, system behavior based attestation can also be used to effectively constrain impacts caused by malicious code such as Trojan and virus which are common in today?s organization business systems.