Abstract: This paper analyzed the performance of vector quantization with codebook comprised of multiple sets of orthogonal vectors in space division multiple access(SDMA) systems with limited feedback. Using probability theory, mathematical expressions for the channel direction information (CDI) vector quantization error distribution were derived considering the orthogonality of codewords. Then the downlink SINR distribution of orthogonal beamforming SDMA systems was obtained. The numerical results show that the analytical deduction is coincident with the actual facts.