Water lock damage is one of the main damage ways in low porosity and low permeability oil and gas fields, seriously affecting the normal exploitation of oil and gas fields. In order to find out the main factors affecting the water lock effect and effective methods to remove water lock damage, the variation of gas permeability before and after the reservoir core water lock was studied and the degree of water lock of rock samples was quantitatively evaluated using the rock samples from the condensate gas reservoir in Jilin oilfield as raw materials, through the indoor water lock damage experiment of reservoir core. The results showed that water lock effect was mainly caused by the water saturation, pore throat radius, the watersensitive illite, Yimeng mixed layer in the clay minerals with high content and hair and tufted convex. On this basis, the effect of methanol, slippery water and N ₂ injection on water lock damage was evaluated. It is proved that N ₂ unlocking effect is the best, permeability can be restored to about 30% of the original, methanol injection unlocking effect is better than sliver water, and the best amount of alcohol injection is 0.4 PV.