Due to the complexity of calculating model for the current optical parabolic surface and to acquire the high-precision surface based on the data of finite element analysis for parabolic surface, a new high-precision algorithm of surface parameter for optical parabolic surface was proposed. Firstly, the discrete error of the optical parabolic surface was proposed, and elimination technique of discrete error was researched, which was also the crucial step for the data preprocessing of the surface parameter calculation. Secondly, the rigid body displacement and surface distortion displacement were distinguished with the data processing algorithm based on rigid body displacement. Lastly, the basic data to obtain parameter, just as the root mean square, was got using the optimal design algorithm. The algorithm realization of the high-precision parabolic surface parameter was discussed and the validity check of the algorithm was performed as well. The result of validity check demonstrated: the high-precision algorithm of parabolic surface parameter is higher, and the check error is about 6%. The precision of new algorithm can satisfy the engineering requirement, and it also provides a new technical reference for the high precision calculation of optical surface parameter under the external thermal load.