The calculation and analysis of the target acquisition probability of image homing rocket is an important part of its combat effectiveness analysis. In order to calculate the acquisition probability accurately, combined with the characteristics of ballistic and the performance of detection equipment, the mathematical model of acquisition probability was established based on hit error theory and Johnston standards, etc The mathematical model includes the probability model of rockets falling into the guided area and the probability model of seeker identifying target. Based on the model the influence factors (including detection height firing data error target size and speed of target motion and so on) of target acquisition probability were analyzed, and some meaningful conclusions were extracted. The conclusions could be applied in the future fight as an important reference.