This study aims to investigate the effect of the Project-based Learning (PjBL) Class Model on Chinese undergraduates' argumentative writing performance. A mixed-methods approach was employed to attain the main objective of the study. It included 50 non-English major students in the control group (25) and experimental group (25) from a Chinese University. The experimental group participants were taught argumentative writing under the PjBL Class Model, while the control group used conventional Presentation, Practice, Production (PPP) Class Model. After a six-week teaching experiment, semi-structured interviews with nine students of different majors from the experimental class were conducted to investigate the PjBL Class Model's influence on argumentative writing and its acceptability. SPSS analysis of pre- and post-tests revealed that the overall writing scores and sub-scores in terms of idea expression, text organization, language use, and writing strategies had been raised significantly. Interview findings showed that students had a strong perception and acceptance of the PjBL Class Model for learning argumentative writing, and compared to the conventional teaching model, it significantly boosted their interest in the subject.