Tackifying and shear strength improving agent as well as preparation method and application of tackifying and shear strength improving agent

The invention relates to a tackifying and shear strength improving agent and a preparation method thereof. The tackifying and shear strength improving agent disclosed by the invention is prepared through the steps of reacting dimeric fatty acid and polyethylene polyamine according to the molar ratio, namely 1: (0.4-1.6) of carboxyl to amino in the existence of triethylene glycol monobuthyl ether, wherein the reaction temperature is 140-160 DEG C; keeping the temperature until no water comes off, and then, further reacting for 10-20 minutes to finish the reaction; and removing water generated by the reaction while reacting. A soilless oil-based drilling fluid system with the tackifying and shear strength improving agent is good in suspension property, enhanced in solid-phase and stratum water pollution resistance, little in reservoir damage, increased in system permeability recovery value, stable in performance, strong in inhibiting property, good in lubricating property, low in plastic viscosity and high in temperature resistance up to 260 DEG C.