The invention discloses a compound cantharis injection preparation and a preparation method thereof, and the compound cantharis preparation is prepared by cantharis, ginseng, radix astragali, acanthopanax, sparganium, herba scutellariae barbatae, rhizoma zedoariae, common macrocarpium fruit, glossy privet fruit, bear bile powder, liquorice and appropriate auxiliary materials. The invention adoptsthe methods of ethanol diacolation or ultrasonic extraction, depositing in water and centrifugation to extract, the extraction effect is good, the operation is convenient, and the stability is good; ethanol is adopted as solvent to extract the rest nine drug ingredients except the bear bile powder and the cantharis; meanwhile, the valid target of total saponin extracted from the nine drug ingredients is purified by adopting the mode of organic solvent exhaustion, so that the compound cantharis medicine has centralized active ingredient and higher purity quotient; the precipitation extracted by the ethanol is purified by adopting the method of macroporous resin absorption, so as to obtain the amylose active ingredient of the nine extracts such as ginseng, and the like, and the obtained amylose components have good pharmacological action and little untoward effect. The compound cantharis injection preparation prepared by the method has the active ingredient with higher content and can achieve the effects of improving the bioavailability.