Learners' experience with writing in general and argumentative textual productions in particular, requires a great deal of lexical and syntactic knowledge that grant them the ability to discover and put into words their ideas.Thereupon, the motivation for conducting this study which is a self-possessed analysis of learners' argumentative essays, is basically to explore the use of substantive words and complex sentences in their argumentative writing at Moulay Ismail University. The book makes an endeavor to examine the extent to which overusing these elements affect their overall scores in textual productions. With regard to the comparative analysis of the results, it is demonstrated that complex sentences are not used numerously in argumentative writing. Students do not give too much interest to this type of sentence. As for substantive words, it can be asserted to some extent that most students use them with a lucid and observed quantity.