The present disclosure relates to a biochemical detection instrument. The technical solution is an automatic reactive oxygen species content detection system suitable for a cell microenvironment that includes: a sample transmission reaction system and a detection system which are communicated in sequence through a light avoiding pipeline. A washing system is in communication with the sample transmission reaction system through a water pipeline, and a purge system is in communication with the sample transmission reaction system through a gas pipeline. The sample transmission reaction system further includes a sample injector and a DCFH supply bin which are communicated with a reaction bin through light avoiding pipelines after being connected in parallel. Sample injection valves are respectively configured between the sample injection valve and the reaction bin and between the DCFH supply bin and the reaction bin.