Abstract: One of the main error sources in orbit dynamic model of the ShenZhou manned spacecraft is due to the effect of deflation,which gives an extra force on the spacecraft.This effect introduces an error in orbit by the order of several kilometers at maximum in the transversal direction.An empirical dynamical model for the deflation process was developed and three model parameters were estimated based on onboard microgravity accelerometer and navigation data.It shows that the precision of orbit prediction is enhanced by over an order of magnitude,indicating that the model is a reasonable solution to the deflation process.