The invention discloses a preparation method of a cigarette filter rod additive. The cigarette filter rod additive takes phlomis betonicoides as a raw material and is prepared through the following steps: (1) preparation of the raw material: drying the phlomis betonicoides at the temperature of 50-80 DEG C, and pulverizing to 50-100 meshes; (2) sub-critical extraction: taking dimethyl ether as an extracting agent and glyceryl triacetate as an entrainer to extract the pulverized phlomis betonicoides powder at the temperature of 0-50 DEG C and under the pressure of 0.5-3.0 MPa; (3) preparation of the filter rod additive: recycling dimethyl ether in the step (2), and obtaining a glyceryl triacetate solution containing a phlomis betonicoides extract, namely the cigarette filter rod additive. The invention further discloses an application of the cigarette filter rod additive obtained through the preparation method to a cigarette product.