A model of surface recombination velocity for n-type Hg1-xZnxTe is presented. It has been shown that, both experimentally and theoretically, the surface recombination velocity is dominated by Shockley-Read recombination mechanism at higher temperature and dominated by Auger process at low temperature. We have further developed a surface recombination theory for the narrow-gap semiconductor. It is concluded that the optimum conditions to reduce recombination velocity is about 2 x 10(11) cm(-2) in the fixed charge density and the Cd0.8Zn0.2Te passivation layer thickness is between 140 and 160nm.