Abstract: his paper studies the reentry guidance rules and the effects of the reentry errors on the landing spot of a spacecraft. Its contents reads as follows: the study of the laws of vertical direction and side direction, to analyze the effect of each error on landing spot; simulation calculating the comprehensive effects of all of errors on the landing spot.It gives the level of the effects of the reentry errors on the landing spot and presents the accuracy levels which the reentry errors must satisfy. The results of simulation prove that the guidance laws can make satisfactory control accuracy of the landing spot.