With picture-word interference paradigm and masked priming paradigm, the present paper investigated the lexical selection mechanism in comprehension for Chinese learners of English through exploring the influences of different semantic relatedness on lexical comprehension. Based on the related assumptions and results, it is concluded that the lexical selection in comprehension for Chinese learners of English is a competitive-interference process. Interference is evoked by competition among non-targets, and the interference effect produced by within-category non-targets is more significant than that produced by those from different categories. Among the within category non-targets, those with different semantic relatedness generate different amount of interference effect. As the interference conditions change, the interference effect differs among non-targets from different categories.