Abstract: The technology of eliminating water lock by nitrogen injection is an innovative trial measure in the northern Tarim condensate gas fields. This paper described the principle of the technology, and discussed some problems such as nitrogen injection volume, well selection criterion, characteristics of construction pressure curve and when to end construction combined with practical engineering case and effect of 4 wells. It is concluded that condensate gas wells with more oil and gas, energy, interlayer, water lock, low porosity and low permeability, no plug and no leakage loss are suitable for eliminating water lock by nitrogen injection. We should end construction when pump pressure is higher than formation pressure.