Based on the shrink-wrapping algorithm, this paper presents an approach to reconstruct Catmull-Clark subdivision surfaces from unstructured triangular meshes. Attracting / relaxing operators are designed using properties of Catmull-Clark subdivision. By presenting the reserving convexity constraint and the flat degree constraint, the base mesh can reserve sharp characters in the simplified triangular mesh and mesh edges do not cross after the base mesh is subdivided. By using these methods, such as the push-back subdivision scheme, the attracting operator and the relaxing operator in quadrangular meshes, the approach need not distinguish sharp characteristic while reconstructing surfaces. It can deal with the whole mesh by the single algorithm. Main components of the approach are constructing base meshes, adjusting vertices of subdivision meshes, choosing subdivision schemes and analyzing errors of subdivision surfaces.