Abstract: Code-switching has long been the focus of bilingual cognitive processing. Researchers have adopted various types of research paradigm to examine the cognitive and neural mechanism of code-switching processing during language production and language comprehension, and they constructed relevant theories and theoretical models. Based on a detailed review of theories and theoretical models concerning bilingual code-switching processing, such as Inhibitory Control Model, interactive alignment model, language-specific selection hypothesis, language-specific selection threshold hypothesis and Bilingual Interactive Activation Model, we analyze the controversies on the sources of switch costs, asymmetry of switch costs and mechanism of lexical selection among these theories and theoretical models. Moreover, issues that should be considered in future studies are discussed and some suggestions are made in terms of research perspectives and methods. It is hoped that the review can broaden the research topic concerning code-switching processing both at home and abroad.