Can mold release agent be used in 3D printing? Do we need mold release agent in 3D printing mold? If it is not used, what effect will it have on the product?
It seems I misread your question.  

3D Printed Mold

You were asking about (or the question now states) use of a mold release compound to prevent a molded part from sticking to a 3d print mold.

Yes.  It is always beneficial for the molded part to not stick to the mold.  Easy separation and part removal is important for the life of the mold and for the surface finish of the part.

There are two molding situations that seem important.  

Flexible Mold or Object

In the first, either the part of the mold is elastic, so the actual sliding of one surface on the other isn't important.  Here, a mold release agent would help by preventing the cast object from binding to the mold material.

Stiff Mold and Object

The second case is where both the mold and the object are stiff, and the object must slide out of the mold.  Here the layer lines should be considered, since there may, locally, be reverse draft angles where the larger part can not slip past an obstructing filament line.  Using a process that doesn't leave filament lines, or using the thinnest possible filament layers, or smoothing the mold internal surfaces, or possibly filling the spaces between the ridges with another material may eliminate the problem.  A "mold release agent" would still be used to reduce the attachment of the object to the mold, although one may be able to use ample release agent both to fill the groves in the mold and prevent adhesion.