A method of preparing polyurethane hot melt adhesive with high temperature resistance generally includes the following steps: (1) adding isocyanate with a silane modifier in a reactor in an inert atmosphere, heating and stirring, then adding chemical dehydrant into the reactor and mixing evenly; (2) adding dehydrated diluent and tackifier resin to the reactor while maintaining the inert atmosphere and heating, adding dehydrated polyester polyol and polyether polyol, stirring, and allowing to react at constant temperature for a predetermined time period; (3) adding dehydrated polyether amine, stirring, and heating; and (4) adding a catalyst, vacuumizing, discharging materials and packaging the materials in an airtight container. The hot melt adhesive made according to the new method has a variety of improved physical and mechanical properties, including improved high temperature resistance, cold and heat shock resistance, drop resistance toughness, high adhesive strength, salt spray resistance and moisture and heat aging resistance.