Maya Modeling :: How To Combine And Mesh Vertex From Middle Of Object

I have problem when i duplicate polygon another side of model. The object is not smooth, it look like different model. I try to "combine" and "mesh" vertex from middle of object. but it still same. The polygon will smooth if i use "smooth tool". But i need low polygon for transfer map from high polygon to low polygon. but it not work, because low polygon look like different model.

I need smooth low polygon, but not to much smooth. I need only when i duplicate polygon, it not look like different model is okay.