A composite perfect electric conductor (PEC)-perfect magnetic conductor (PMC) metasurface is proposed for orbital angular momentum (OAM) generation. Each scatterer on the metasurface consists of an anisotropic PEC layer and an isotropic PMC layer. Unlike conventional metasurfaces that composed of discrete scatterers, the scatterers on the proposed metasurface form a quasi-continuous pattern. Therefore, negative consequences of periodicity breaking from the patterned scatterers with varying sizes or orientations and their mutual coupling are avoided. We model the scatterer using Jones matrix. Its design is based on the features of PEC and PMC, which abandons complicated optimization process. The patterning of scatterers on the metasurface is determined by a grating function. The designed metasurface reflects the incident left circularly polarized (LCP)/right circularly polarized (RCP) plane wave to a RCP/LCP vortex beam carrying OAM, with nearly 100% efficiency.