Background: It is reported that 30% to 80% schizophrenia patients suffered from hypersalivation when taking clozapine. Some investigations of the use of formulas of traditional Chinese medicine (TCM) to treat clozapine-induced hypersalivation suggested their potential treatment effects. In these formulas, Suoquan Pill (SQP) and Wuling Powder (WLP) were suggested to have therapeutic effects in improving clozapine-induced hypersalivation. Methods and design: A prospective, double-blind, randomized, placebo-controlled study will be conducted to test the therapeutic effects of SQP and WLP in relieving hypersalivation in patients taking clozapine. A total of 45 patients will be enrolled into this study with 15 in each treatment group. Patients will receive medication according to their assigned group. Either SQP 10 g per oral dose twice daily, WLP 10 g per oral dose twice daily or placebo powder 10 g per oral dose twice daily will be prescribed to the patients for 8 weeks. The Drooling Severity Scale, Nocturnal Hypersalivation Rating Scale and sialoscintigraphy will be used as the primary outcome measures; the Clinical Global Impressions Severity, the Positive and Negative Syndrome Scale, the Abnormal Involuntary Movement Scale, the Simpson-Angus Scale and the TCM constitutional scale will be used as the secondary outcome measures Discussion: It is hypothesized that SQP and WLP will have a beneficial effect in controlling clozapine-induced hypersalivation symptoms. It may also improve the life quality of psychotic patients by improving their mental status. Trial registration: ClinicalTrials.gov (Identifier: NCT01045720).