Abstract: The interpretation of the "semantic P600" effects triggered by sentences which are grammatically correct but contain mismatched semantic roles is one of the hot topics in the ERP study of sentence processing. For more than ten years ever since their discovery, there have been two competing models, namely the multi-stream and the single-stream model in accounting for the "semantic P600" effects. These two models had a vehement debate over whether semantic processing is independent from the syntactic one and over the functions of P600 components. This paper firstly introduces the origin and influence factors of "semantic P600 effects". Then, it combs through and compares the theoretical stances and supporting empirical evidences of the two models, pointing out that what the "semantic P600 effects" reflect might be the relationship between language and other modules in our cognition. Finally it points out the directions and tendencies in relevant studies.