This study aimed to explore the effects of writing portfolio on English writing performance of non-English majors. Both quantitative and qualitative methods were used. 127 second-year students in the major of international business participated in this study. They were divided into the experimental group and the control group. The methods of data collection consisted of writing tests and interview. Writing portfolios were implemented in the experimental group while the control group did not use them. The quantitative data suggested that there was no significant difference between experimental group and control group in English writing performance after the treatment. However, the qualitative data indicated that most of the participants had positive attitudes towards writing portfolios.
