Objective To explore the effect of medical game intervention based on the broaden-and-build theory on improving the emotional and behavioral problems of children with hematological tumor. Methods A total of 36 children with hematological tumor hospitalized from June to December 2020 were selected as a control group, and another 36 children hospitalized from January to June 2021 were taken as an experimental group. The control group received routine game intervention, while the experimental group additionally received medical game intervention based on the broaden-and-build theory. Before the intervention and 8 weeks after the intervention, the Strengths and Difficulties Questionnaire was used to evaluate the effect. Results After the intervention, the total score of emotional symptoms, hyperactivity, inattention, conduct problems, peer communication behavior, difficulties and prosocial behavior between the two groups were significantly different (P<0.05, P<0.01). Conclusion The medical game intervention based on the broaden-and-build theory can effectively improve the emotional and behavioral problems in children with hematological tumor.