To offset the scantiness of exterior trajectory measure in interstage section, interstage trajectory reconstruction model was built using telemetry apparent acceleration and exterior trajectory parameters at a time before interstage section: Precision estimation method of exterior trajectory is built to locate the start boundary, and evaluate the reconstructed trajectory; Error correction model of telemetry apparent acceleration was built to reduce the influence by measurement error on reconstruct trajectory; Genetic algorithm was used to optimize the parameters of the apparent acceleration error model, and use the comparison between reconstruct trajectory and exterior trajectory to design objective function. The results show that, error correct model of apparent acceleration after parameters optimized improve the reliability of reconstruct trajectory effectively; The error sources of apparent acceleration are coupled, the solution of error correct model parameters is not unique: Acceleration of reconstruct trajectory has the same trend with telemetry acceleration, meets the exterior precision requirement.