The invention relates to a preparation method of a composite cigarette filter, and belongs to the technical field of cigarettes. The method comprises the steps that firstly juncus roemerianus fiber ispretreated by adopting a mixed solution of isopropyl alcohol and water, and then the pretreated juncus roemerianus fiber is subjected to suction filtration under the infiltration of water/ethyl alcohol mixed solution of polyvinylpyrrolidone and freeze-dried to obtain the modified juncus roemerianus fiber; then, the modified juncus roemerianus fiber is cut into strips and granules respectively, and strip type and granular type filter materials are obtained through pressing and coating by adopting a filter rod forming machine; finally, the strip type and granular type filter materials are cut and end-spliced, co-pressed by the filter rod forming machine and then coated with filter forming paper to obtain the desired composite cigarette filter. The composite cigarette filter has the advantages that the structure is simple, the materials are natural and degradable, and the product has significant tar reduction and harm reduction effects under the multiple action of physical porous channelinterception, chemical complex adsorption and interface delay filtration.