The reserves of low-permeability oil reservoirs in our country is abundant. How to further improve oil recovery after water flooding in low-permeability reservoirs is one of the technical challenges faced by this type of reservoir. In recent years, gas injection to improve oil recovery technology has received widespread attention both domestically and internationally. Gas injection miscible flooding can achieve oil recovery efficiency of over 90%, and has great potential to improve oil recovery. In order to evaluate whether gas injection in low-permeability light oil reservoirs in Tuha can achieve a mixed phase state, indoor experimental research was conducted. Eight blocks of crude oil in Tuha low-permeability light oil reservoirs were injected with three different gas sources (CO2, Shanwu pipeline gas, West East Gas Pipeline gas), and the oil displacement process and minimum mixed phase pressure (MMP) were evaluated to analyze the influencing factors of mixing. The result has shown that under existing formation pressure, Tuha light oil is prone to mixing with CO2, while injecting hydrocarbon gas (such as Shanwu pipeline gas or West East Gas Pipeline gas) increases the minimum mixing pressure (more than 10MPa higher than pure CO2 flooding MMP), making it difficult to form mixed phase flooding. It is suggested that the Pubei block of Tuha Oilfield adopt mixed phase drive with Shanwu pipeline gas injection, mixed phase drive with West East gas transmission gas injection in Yuguo block, and mixed phase drive with CO2 gas injection in other blocks, which can achieve good development results. Technical support is provided for the implementation of mixed phase gas flooding in low-permeability light oil reservoirs in Tuha Oilfield.