Four available satellites are needed in traditional 3D positioning method based on pseudo-range measuring. Aiming at reducing the needed satellites to enhance the adaptability of the navigation algorithm, in view of the cumulative characteristics of the INS error which can be seemed as a constant in single short period, the problem of calculating missile position and velocity which is varied with time was converted to calculating INS error which is constant in single period. Therefore, 4 satellites measuring could be replaced by 4 times measuring to the same satellite and the measuring equations were built to realize the positioning and velocity measuring using one satellite. The performance of the method in this paper was inferior to traditional method, because its navigation period was longer and the additional error was induced by regarding the INS error as a constant in a single navigation period, but the simulation result shows that the method of this paper can guarantee navigation precision to a certain extent.%基于伪距测量的卫星导航方法，实现3D定位测速至少需要4颗可观测卫星。为减少所需可观测卫星数量以提高导航算法的适应性，利用惯导误差不断累积的特性，在单个较短导航周期内将惯导误差看作常值，将直接求解导弹位置和速度转化为对惯导误差的求解，从而将未知数由时变量转化为短时间内不随时间改变的量，以适应用多次测量代替多星同时联测，构造观测方程实现单星定位测速。由于导航周期为4个观测周期，比多星导航方法导航周期长，且将单个导航周期内惯导误差看作常值，引入了额外误差，但仿真结果表明，仍能在一定程度上保证导航精度。
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