The hole structure has great impact on the performance of polymeric film materials. In the current work, we focused on the formation mechanism and control of nascent holes that frequently appeared when preparing polymer films on poor wetting substrates. Number density and dewetting area of nascent holes on nanofilms of two model polymers, polystyrene and polymethyl methacrylate prepared from various solvents and spincoating conditions, were systematically studied. Sufficiently large spin speed and prolonged immersion time demonstrated both inducing more and larger holes as a result of high capillary stress and chain adsorption at the surface, respectively. Moreover, solvents played the most critical roles on the formation of nascent holes. Faster evaporative, intermediate Hassen parameter between the polymer and the solvent, and smaller surface tension of solvents promote the formation of more intact films. This work provided deeper understandings on the formation mechanism of polymer nanofilms and an effective approach for controlling nascent holes, which were both of particular importance in the fabrication of functional organic thin-film materials.