In recent years, mobile ad hoc networks (MANET) have become an interesting research area. This type of networks have a salient characteristics compare with wired networks which are more vulnerable. Nowadays, for the network security, defend in depth strategies are used. One of them is intrusion detection system (IDS). Many intrusion detection techniques developed for weird networks however, because the nature of MANET we cannot apply them directly in MANET. According to detection techniques, IDSs can be classified into three categories as follows: Misuse-based detection, Anomaly-based detection, and Specification-based detection.In this paper, we are going to evaluate anomaly-based intrusion detection techniques proposed for MANET. For this, we present a comprehensive survey about anomaly based intrusion detection techniques. Afterward we evaluate their performance, advantages, and disadvantages. As a result constantly, we will understand MANET's security problems based on which we can suggest solutions for future research.