The invention discloses a melamine modified resin adhesive for flax chip shaving boards, and a preparation method thereof. The resin adhesive comprises, by weight, 1230-1600 parts of formaldehyde, 1050-1300 parts of melamine, 40-80 parts of diglycol, 30-80 parts of caprolactam and 700-1000 parts of water. Melamine is used to substitute urea in order to be used for synthesizing melamine-formaldehyde resin, so the colorless and semitransparent properties of resin are reserved, and the resin adhesive also has the advantages of suitable storage period, controllable cost, improved water and heat resistance, and solidification at normal temperature.