Abstract: The RGRR parallel two-degree of freedom rotating mechanism has the advantages of high stiffness, high load capacity and compact structure. In this paper, the static stiffness matrix of RGRR mechanism in fixed coordinate system is obtained by the mapping relationship between the external load on the end output member and the deformation of the end output member. Through Matlab calculation and analysis, the distribution law and sensitive direction of the static stiffness of the mechanism in its working space are obtained. This paper provides a reference for the static stiffness research of other parallel mechanisms.