In the flight test of target indication system, we are faced with the problem of how to evaluate the effect of the error of target indication system on its operational capability while evaluating its index conformance. In order to study the method of evaluating the precision and capability of target indication system, the relationship between target indication error and weapon strike effect is analyzed, and the error model of target indication system based on current point attack and predictive point attack mode of surface warship is established. The relationship between the target indication error and the weapon acquisition probability is transformed into the relationship between the target indication error and the probability of the missile terminal falling into the designated area. The results show that the target indication errors under the two attack modes obey the two-dimensional normal distribution. When the target indication errors increase, the probability of Weapon Acquisition decreases significantly. If the effect of weapon attack is to be guaranteed, the lower limit of target indication error is corresponded. The lower limit provides a reference for the flight test method of ship-based helicopter long-range target indication system