The compression deformation behavior of 316LN austenitic stainless steel was investigated at 1050~1200 °C under strain rate of 0.1, 1, 50 s^-1. The influence of deformation temperature and strain rate on the hot flow curves was analyzed. Based on the dislocation density theory, the hot deformation constitutive model of 316LN steel was established. The softening mechanism of the 316LN steel was revealed. The results show that the dynamic recrystallization (DRX) dominates the softening mechanism under the condition of high temperature and low strain rate (<0.1 s^-1); the dynamic recovery (DRV) dominates the softening mechanism under the condition of high temperature and high strain rate (>1 s^-1); DRX and DRV dominate the softening mechanism under the condition of high temperature and strain rate of 0.1, 1 s^-1. The established constitutive model can precisely predict the hot deformation behavior of 316LN steel: its Pearson correlation coefficient is 0.9956 and the average absolute value of relative error is 3.07%, indicating the accuracy of this constitutive model.