Abstract: As a cross discipline of agroforestry and medicine, horticultural therapy has been proved to be effective in the treatment and rehabilitation of children with autism spectrum disorder (ASD) without any side effects. Western developed countries have paid close attentions to horticultural therapy and have already formed relatively perfect treatment standards and system of it. Very few domestic experiments and clinical reports of horticultural therapy can be found, and it is mainly focused on design and plan of healing garden, less concerned about other forms of horticultural therapy; in other words, the scope of the study is relatively narrow. The rehabilitation mechanism of horticultural therapy is mostly focused on psychology and landscape architecture design. From the perspective of sociology, ecology and physiology, this paper explores the rehabilitation mechanism of horticultural therapy. What is worth mentioning is that forest therapy in domestic research rarely involved, and is often integrated into the environmental health sciences. However, in fact, from the view of treatment methods and effect mechanisms, forest therapy should belong to the category of generalized horticultural therapy, thus it is also discussed in this paper. Analyzing the various forms and multiple mechanisms of horticultural therapy in the treatment and rehabilitation of children with ASD, provides a more complete theoretical basis, aiming at promoting the development of domestic horticultural therapy and relevant clinical researches and applications.