Natural plant composite particles with sweetening and moisture-preserving functions and a preparation method and application thereof are provided. The composite particles which are 30-60 in mesh are prepared by: crushing Poria, Momordica grosvenori fruit, root of Angelica sinensis, florists chrysanthemum, honeysuckle, flowering tobacco, licorice root and Pinellia ternata tuber separately, performing cell disrupting, screening to obtain cell-broken powder, adding auxiliaries to the cell-broken powder, mixing well to obtain a mixture, adding a certain amount of water into the mixture to obtain wet material, subjecting the wet material to rotary granulating, drying at low temperature, stabilizing the size, and screening; based on existing rich plant materials and long-standing studies and application history, the plant materials with sweetening and moisturizing functions added herein feature zero harm, zero additives, zero pollution and good safety and reliability and have the functions,such as aroma enhancing, disinfecting and antioxidation; the plant materials do not combust, so that harm harmful matters are avoided; by adding the prepared composite particles to a cigarette filter,effective active ingredients of plants themselves can be retained.