The conventional drainage gas recovery and water-controlled gas recovery techniques are difficult to solve the problems of low porosity，low permeability，and small pore throats in tight gas reservoirs. For this reason，the phase inversion technology is utilized to prepare nano-drainage agents suitable for tight gas reservoirs to change the rock surface characteristics and improve the drainage effects of tight gas reservoirs. On the basis of self-prepared nano-drainage agents and tight cores，this paper explored the action mechanism of nano-drainage agents to core slices and their powder by modern testing technology and evaluated the effects on core wettability and microscopic morphology. The drainage gas recovery action mechanism of nano-drainage agents was then discussed. The results show that instead of reacting chemically with the core surface，the nano-drainage agent is only adsorbed on the core surface by electrostatic and hydrogen bonding effects to form a hydrophobic film，which can reduce the core surface roughness and the flow resistance in the pores to achieve drainage gas recovery. At the same time，the nano-drainage agent can reverse the core wettability in the reservoir，namely that the capillary pressure becomes a resistance to prevent the discharged formation water from flowing into the reservoir again，extending the validity period of drainage gas recovery.