The invention relates to a compound liquorice tablet and a preparation method thereof. The compound liquorice tablet is prepared from the following components in parts by weight: 180.0 parts of liquorice root extract powder, 6.4 parts of opium powder, 3.2 parts of sodium benzoate, 3.2 parts of camphor, 3.2 parts of star anise oil, 0.1-37.5 parts of an adhesive, 1.3-52.7 parts of a flow aid and 5.6-38.0 parts of a moisture-proof agent. The materials are mixed according to certain steps and sequence, a dry granulating method and a wet granulating method are combined, and tabletting is performed to obtain the compound liquorice tablet which is stable in quality, good in moisture-proof property and relatively good in mouth feel; the process is low in equipment requirement and suitable for long-time production in production workshops; in addition, the process is stable and does not depend on a tabletting machine.