The invention discloses a system and method for treating comprehensive wastewater in chemical industrial parks, belonging to the technical field of wastewater treatment. The treatment system disclosed by the invention comprises a biochemical treatment system and a high-concentration wastewater pretreatment system, wherein a water collecting pool, a hydrolyzing pool, a primary settling pond, an A/O biological treatment device, a secondary settling pond and a coagulation settling pond are sequentially connected in the biochemical treatment system; an iron carbon micro-electrolysis mechanism, a Fenton oxidation mechanism and a neutralization and sedimentation mechanism are sequentially connected in the high-concentration wastewater pretreatment system. The treatment method disclosed by the invention comprises the following steps that: 1, wastewater enters the water collecting pool and then is subjected to water quality adjustment; 2, low-concentration wastewater is treated by the hydrolyzing pool, the primary settling pond, the A/O biological treatment device, the secondary settling pond and the coagulation settling pond so as to be discharged; 3, the high-concentration wastewater is treated by the iron carbon micro-electrolysis mechanism, the Fenton oxidation mechanism and the neutralization and sedimentation mechanism, then flows into the water collecting pool, and then is treated again. According to the invention, high-concentration wastewater and low-concentration wastewater are distinctively treated, so that discharged water subjected to treatment completely can reach the emission standards of sewage treatment plants.