This document describes research on developing a new solid insulation paper for oil-immersed transformers using phenol formaldehyde resin. Samples of kraft paper were prepared with one-side layering and double-side layering of phenol formaldehyde resin. Testing showed the electric strength of the paper improved in oil, with the double-sided sample performing best with a dielectric strength of 70.3 kV/mm in oil. The research demonstrated layering phenol formaldehyde resin on kraft paper enhances the insulation properties of the paper, particularly for use in oil-immersed transformers.