Abstract: The problems met during the coalescence of fluid drops (liquid or gaz) in chemical reactors or other, brought ourself to study the dynamics of drops put on an inclined solid plane. The first part of this study is consecrated to characterize the fluid-solid interfaces by a certain number of parameters which could be introduce in the equations of topic. The spreading of the drops then described. In the second part, this study resolve non linear partial differential equations of second order giving the difference profiles of the sessible drop on the horizontal plan and then tilted. The crawling of the drop of the tilted plan is described. A valuing of critical volume of the drop in function of the angle of slant is expressed.