Abstract: The stress relaxation experiments under the conditions of deformation temperature of 600-950 ℃ and strain rate of 1 s-1were conducted on the vanadium microalloyed steels with different carbon content of 0.26wt%, 0.33wt% and 0.42wt%, and then the stress relaxation curves of the steels and the precipitation kinetics (PTT) curves of V(C,N) were obtained. Combining with the microstructure, the precipitation law of V(C,N) was analyzed. The results show that the precipitation of V(C,N) inhibited the recrystallization of austenite in the tested steels, resulting in the decrease of stress. The PTT curves of V(C,N) precipitates in austenite showed a S-like shape. The precipitation rate of V(C,N) was the fastest at 900 ℃. The increase of carbon content in the tested steels accelerated V(C,N) precipitation rate, but had no effect on the temperature with the fastest precipitation rate. The tested steel with the highest carbon content had the shortest precipitation start time of 7.5 s.