Abstract: According to the theory of B-spline, the G2 coti nuity conditions between two patches of special NURBS surfaces, namely bicubi c uniform rational B-spline surfaces have been discussed, meanwhile, the suffic ient and necessary conditions of G⁰ are given in this paper, in order to satisfy the need of application, a special kind of sufficient conditions of G² continuity have been provided in the end.

Key words: NURBS surface, uniform B-spline basis function, G² continuity, sufficient and necessary conditions