Abstract: The friction drag coefficient and form drag coefficient for the supercavitating body with different cavity profile were obtained by numerical simulation. With the empirical formula of drag coefficient based on the commonly streamline submerged body, the formula for the supercavitating body was modified to match with those of the numerical results. Using the formula, a software for underwater trajectory prediction was programmed. The underwater trajectory of the all-wetted supercavitating body were predicted by the software is consistent with the experiment results. It is shown that the modificatory formulae obtained by numerical calculation are reasonable.