A trustworthiness-based ad-hoc secure interoperation method is proposed, in which the concept of trustworthiness is introduced to describe the probability of proper collaboration. The trustworthiness of an autonomic domain on a user is decided jointly by direct experiences of interactions and other domains’ assessments on the user. Only the users who satisfy the requirements of target domains’ trust policies have the privileges to access entry roles. Records of a user’s malicious actions will decrease his trustworthiness and then accordingly reduce his privileges. Target domain uses weighted majority algorithm to update recommender’s trustworthiness, which is reduced by unfair ratings. Experimental results show that this method can effectively resist cheating and malicious actions.