Theoretical representation of gear contact condition and transmission characteristics is crucial to attempt design optimization which requires systematic iterative calculation for performing trial-and-error calculation on various combination of design variables. In this paper, a systematic and straight forward theoretical gear meshing analysis methodology considering the occasion of elastic deformation of teeth is proposed, and some important meshing characteristics will be revealed and discussed with practical numerical examples. Validity of the calculation result is evaluated by being compared with experimental measurement results. In the proposed method, gear teeth are modeled as stacks of thin pillars with continuously-changing width from bottom to top, according to the involute tooth profile. Based on this model, meshing condition of multiple teeth taking the elastic deformations of them into account is analyzed. Then, iterative calculation is carried out under four constraint conditions. As the result of theoretical calculation and experimental measurement, validity of the proposed methodology is demonstrated.