The outbreak of the COVID-19 pandemic has caused increasing concern over health care, part of which involves the role of nutrition. In this study, a nutrition educational board game, featuring quantitative computation, was designed to help students acquire nutrition knowledge and improve dietary behaviors. A group of 22 students in grade 7 of a middle school in Beijing were selected as the participants. A single-group pre- and post-test quasi-experimental design was adopted. Knowledge-Attitude-Practice (KAP) questionnaires and interviews were used to investigate students' changes in dietary knowledge, attitude, and behavior. The influence of gender and body mass index (BMI) on the teaching effectiveness was also explored. The results showed that some dimensions of knowledge, attitude, and behavior significantly increased in the students. Their changes in behavior were mainly related to some aspects that were easier to adjust. In addition, the study also found that females and students with abnormal BMI were more likely to be influenced by the educational game to make positive changes in attitude and behavior.