Problem with model rendering

Then i rendering some face cut in 2 triangle but in solid , texture or game mode all fine how fix this rendering problem ?

After rendering face cut in 2 triangle.

Renderers only render triangles so any non triangular faces in your model are triangulated at render time. If the face is planar you won’t see these triangles but if the plane is non planar as in your model they will be visible
You can use smooth shading to visually smooth the edge between two faces but you may want to use an edge split modifier or autosmooth to control what you want and don’t want smoothed