In order to calculate the engineeized disturbance rejection rate(DRR) amplitude index accurately, the terminal guidance loop was introduced into the model of disturbance rejection rate parasitic loop. For the influence of the positive feedback disturbance rejection rate amplitude under the six common error models, a calculation method of terminal guidance time remaining used for working in the guidance loop was presented. These were classified to three types for the constant target maneuver and initial angle error, random target maneuver, glint noise and faded and receiver noise, the relationship of relative speed ratio, the disturbance rejection rate amplitude and dimensionless miss distance was obtained, and the disturbance rejection rate amplitude index was estimated by the overall judgment of the miss distance value time, margin limits, miss distance change trend and practical value, which provide references for engineering application.