During the development of CO2 flooding in low permeability reservoirs，the most serious problem is gas channeling. At present，there are no quantitative gas channeling identification standards，and the existing calculation methods of gas channeling volume are not practical. The dynamic variation characteristics of CO2 content in the produced gas are analyzed，and the types of gas channeling are divided into the obvious gas channeling and the weak gas channeling. The calculation method of gas breakthrough time is determined，and the identification and evaluation criteria for gas channeling are established. On this basis，gas channel volumes from the injection side and the production side are calculated respectively by using the principle of material conservation. In order to eliminate the influence of single well fluid production ratio or pattern shape factor on the gas channel volume，the gas channel volume is corrected by the gas channel volume intersection diagram. The calculation method of gas channel volume has strong operability and practicability according to the results of gas channeling wells in a tight reservoir. On one hand，this method realizes the qualitative evaluation on gas channeling type and gas channeling degree. On the other hand，this method realizes the quantitative calculation of gas channeling volume and gas channeling horizontal area. It can provide theoretical basis for reasonable design of plugging measures and dosage of plugging agent in the later development stage.