In order to solve the problem that naval gun can not conduct virtual calibration for long-range sea firing because the impact water column is beyond the range of tracking radar, a method of long-range virtual calibration for sea firing based on fixed virtual point is proposed. The longitude and latitude coordinates of the launching ship and the virtual point are determined; The position of the impact water column is measured, and the longitude and latitude coordinates of the water column are calculated; The deviation of the impact water column relative to the virtual point is calculated. The simulation results show that the shooting accuracy can be improved significantly by first test-firing the virtual point and then shooting the long-range target on the sea according to the model.