Resin-modified method epoxy resin and preparing method

The present invention relates to a kind of epoxy-phenolic resin modified by rosin and its preparation method. The said epoxy-phenolic resin has the above structure, in which R represents H or nonyl, n=1,2...10. The preparation method, firstly, melts resin, and feeds phenol or nonylphenol, formaldehyde and ZnO or MgO catalyst under the protection of nitrogen, then after refluxing for some time, warms and vacuum dehydrates to obtain the epoxy-phenolic resin modified by rosin; feeds epichlorohydrin and catalysts, after reacting for some time, vacuum distillates and feeds organic solvents to dissolve; drops alkali solution used in closed-loop or slowly feeds solid bases or metal oxides both fine grinded, after reacting for some time, washes to neutral by water, then distillates and recovers the solution to obtain brown transparent epoxy resin products. After solidifying, the products have better heat resistance and electrical insulation property, and are applied to electronic packaging, coatings, etc.