Abstract: In this paper, expressions of bias B（\hatR_\mathrmo) and mean squre errors MSE （\hatR_\mathrmo） of the combined ratio estimator \hatR_\mathrmo in stratified, random sampling have been got, usability of this estimator has been proved, and the order of bias between this estimator and primary part of MSE （\hatR_\mathrmo） has been given. These problems come from a real back ground. Finaly, some practical computable results have been listed.