Pervasive computing environment is a highly dynamic distributed environment in which principals collaborate spontaneously and unpredictably. Therefore, the pervasive computing puts more emphasis on the role of trust and puts forward higher request to system security than traditional calculation. A new dynamic collaborative trust model composed trust-reputation module and risk module was proposed based on combining credence elements and information safety risk assessment. This model resolve the limitations in the integrality of evidence used for the trust judgment, and in favor of setting up the reliable trust relationship in the entities, and improving environment and information security of universal.