The invention provides a preparation method of 3,4,5-trifluoro-2'-nitro-1,1'-biphenyl. The method comprises the following step: performing a decarboxylation coupling reaction on o-nitrobenzoate shown as a formula I and halogeno benzene shown as a formula II in the presence of a catalyst to obtain the 3,4,5-trifluoro-2'-nitro-1,1'-biphenyl, wherein X1 is a metal cation; X2 is any one of Cl, Br or I. The preparation method has the advantages of use of cheap and readily-available raw materials, avoidance of preparation of an arylboronic acid compound, short synthesis step, higher yield, high product purity, low production cost, no harsh reaction conditions, low equipment requirement, little emission of three wastes, only emission of carbon dioxide and inorganic salts, safety and environmental friendliness, and is suitable for industrial production.