Based on mother tongue transfer theory and contrastive analysis of English and Chinese conjunctions, this paper explores conjunction errors in English writing made by ESL students, which are under the influence of their mother tongue. After writing down and analyzing students’errors, this paper illustrates students’ conjunction errors under the blocking and interventional interference from mother tongue, involving leaving out conjunctions, mechanically applying the rule of Chinese conjunctions and conjunctive collocation. Finally, based on the above conjunction errors made by students, this paper puts forward two pedagogical implications.