Abstract: Pupils have different degrees of anxiety and their attention level is relatively low due to restricted cognitive development. Horticultural therapy, as an ecological psychological treatment method, has a significant effect on anxiety and attention. There have been many experimental and clinical studies on horticultural therapy abroad, and a complete theoretical system has been established. However, few domestic scientists have relevant experiments and clinical reports. This study used both quantitative and qualitative analysis methods to explore the effect of horticultural therapy on pupils' anxiety and its internal mechanism. After analyzing the attention and anxiety of primary school students through the questionnaire survey, we designed horticultural group activities and explored its effect on improving primary school students' anxiety and attention. In addition, we also explored whether attention is the mediating variable. The results show that the primary school students do have anxiety and their attention level can significantly negatively predict anxiety. The anxiety level of the experimental group was significantly reduced and the attention level was significantly improved by participating horticultural activities. However, the mediating role of attention is not significant in the effect of the horticultural on anxiety. In qualitative analysis, we found that horticultural can also bring happy mood, relieve anxiety, improve problem-solving ability, improve attention and concentration, which is of great significance to mental health.