In this paper, we use a discrete Markov chain model to analyze the throughput of CSMA/CA protocol in a wireless local area network considering the capture phenomenon, which means the packet with the strongest power may capture the receiver even in the presence of other overlapping packets. The model of capture effect over the theoretical throughput of CSMA/CA protocol in the presence of path loss, shadowing, and Rayleigh fading is obtained and compared with the model without the capture effect.