In order to explore dynamic monitoring technologies suitable for deep reservoir with high temperature and low permeability, as well as knowing the gas spread range, miscibility state and downhole technical status of CO2 flooding in GX fault block of Jidong Oilfield, several tests such as inter-well monitoring, production logging and well testing were carried out. The test safety problems such as corrosion, high pressure and wellbore clogging were overcome through research. Meanwhile, using dynamic data such as gas phase tracer, gas suction profile and formation pressure test, combined with analysis of geological data and production data, the reservoir connectivity and gas spread range were determined, and the miscibility state was defined. Research results show that the GX fault block has good connectivity. Rapid gas channeling was seen in first-line wells and areas with good physical properties. The spread range was expanded by shutting down gas channeling wells. Vertical thickness of suction after gas injection is larger than that during water injection, which indicates that gas injection increases the production of low permeability layers. After 1 year of gas injection, the fault block reached the miscible condition in the spread range. At the same time, testing technologies such as fluoride, thermal mass flowmeter and 3.2 mm anti-corrosive steel wire were selected, which accumulated experience for dynamic monitoring of CO2 flooding in the same type of reservoir in Jidong Oilfield.