Subject preference is a kind of word-order effect during sentence comprehension, which refers to the following three processing tendency: (a) Ambiguous initial arguments tend to be analyzed as subjects; (b) Initial subjects are easier to process than initial object in unambiguous sentences; (c) Subjects are easier to extract than objects in relative clauses. In the present paper, we mainly discussed three aspect of this preference effect: 1) by analyzing various Indo-European and non-Indo-European languages, we talked about this effect’s particularity and universality; 2) different models of subject preference were discussed, which included the working memory principle, the syntax dependency theory, the prominence principle and the influence of frequent; Third, we also summarized several subject preference-related ERP (Event-related potential) components, and discussed the underlying cognitive processes of each component in the first part; Finally, we pointed out the future directions of subject preference study.