A great temperature gradient easily occurred in the curing process of the thick wall carbon fibers/phenolic composite, usually caused an uneven curing.This paper focused on the research of temperature change inside this kind of product during curing through a temperature monitoring experiment by immersion a thermocouple inside of the product. Meanwhile, the curing reaction behavior of phenolic was studied by DSC technique and gel test. Experimental results showed that internal temperature of product was much belower than inside of autoclave during the early stage of raising temperature.The resin flew better with increase of temperature, and exothermic polymerization began when the resin gel at 95℃ to 100℃.Then the curing system is optimized according to the experiment results,including extend holding time of each temperature,delay the heating rate at early time,adjust the time of total pressure and increase preservation at gel.In the end,the verification is conducted.The results show that optimized curing system is reasonable,a great decrease of defect is confirmed by ultrasonic detector and the quality uniformity of product is improved effectively.