The work aims to study the deformation force features of the paper sheet which is passing through the overlap separation mechanism to provide basis for its kinetic friction analysis. Firstly, the formula was derived to obtain the normal separation condition of paper sheet. Then, with the paper sheet as the elastic beam model, the deformation force acting on the paper sheet surfaces was analyzed with the Clapeyron’s theorem of three moments. The results showed that the deformation force of paper sheet in the overlap area was proportional to the overlap. The wider the gate-roller was, the greater the deformation force was. The deformation force decreased and then increased with the increase of the edge distance of the gate-roller and feed-roller at the left side. The width of the feed-roller had hardly any effect on the deformation force. Based on the analysis of elastic beam model, the law of influence of paper sheet's deformation force in the overlap area changing with the structural parameters is obtained and the values of the edge distance of the gate-roller and feed-roller at the left side are acquired to provide reference for the design of overlap mechanism.