BACKGROUND:　Compared　with　traditional　e-commerce,　a　significant　feature　of　social　commerce　is　the　more　complex　network　of　social　relations　built　by　the　user　through　frequent　online　interaction　and　communication.　This　relationship　network　strengthens　the　impact　of　social　interaction　on　its　purchase　behavior　and　highlights　the　necessity　to　study　social　interaction　in　social　commerce.　OBJECTIVE:　This　research　aims　to　study　the　mechanism　of　social　interaction　on　the　purchase　behavior　of　social　commerce　consumers　based　on　the　SOR　theory.　METHODS:　This　research　uses　SEM　to　perform　hypothesis　testing.　The　survey　data　of　622　consumers　are　used　to　conduct　empirical　tests　on　the　hypothesis　proposed　in　the　research.　RESULTS:　The　research　results　show　that　user-website　interaction,　user-seller　interaction,　user-user　interaction,　user-online　friend　interaction　can　significantly　enhance　users＇　physical　presence;　user-seller　interaction,　user-user　interaction,　and　user-online　friend　interaction　can　significantly　enhance　users＇　social　presence;　other　variables　can　significantly　enhance　users＇　flow　experience　except　for　the　user-seller　interaction;　the　physical　presence　and　social　presence　significantly　affect　users＇　impulsive　purchasing　intention,　but　have　no　significant　effect　on　repeat　purchasing　intention;　the　flow　experience　significantly　affects　users＇　impulsive　purchasing　willingness　and　repeat　purchasing　willingness.　CONCLUSION:　By　connecting　social　interaction　theory,　presence　theory,　flow　experience　theory　with　consumer　purchase　behavior,　the　research　group　provides　a　new　lens　for　how　social　interaction　influence　consumers＇　purchase　behavior　in　social　business　platform.　The　social　business　platform　can　learn　from　the　research　results　of　this　paper　and　formulate　corresponding　measures　to　promote　its　own　development.　©　2021　-　IOS　Press.　All　rights　reserved.