In order to analyze the effect of radome slop error on miss distance, the model of guidance loop including the radome slope parasitical loop was constructed for the first time. The dimensionless guidance loop including radome slope parasitical loop and quadratic seeker and autopilot model was built and the dimensionless miss distance expressions driven by various noises were presented. The stability boundary of parasitic loop and the dimensionless miss distance plot were presented. The simulation results show that smaller damp ratio of guidance system is more sensitive to the radome slope and negative radome slope makes bigger miss distance than the positive one.