中文摘要：

考虑到空间平面圆本质上是由空间平面与球面相交而成，提出了以空间平面方程与球面方程作为约束条件，直接解算空间平面圆的观测方程，导出了相应的解算公式。并以某空间圆形物体的实测数据为例，证实了该方法的实用性。

英文摘要：

The traditional method for space plane circle fitting includes two steps. The first step is to determine the space plane equation and transform the coordinate system into another coordinate system where z axis is perpen- dicular to the space plane. Secondly, the plane equation of a circle is fitted according to the x and y coordinates. Considering the space plane circle is essentially constructed by space plane and spherical plane which is intersec- ted, an approach which takes a space plane equation and spherical equation as the constraint condition has been put forward, which includes directly calculating space plane circle observation equation and the corresponding cal- culation formula. The measured data of a certain space circular object is taken as an example to verify practical application of the method.