Objective To study the effect of ratanasampil (RNSP) which is Traditional Tibetan Medicine on the levels of serum β-amyloid protein, interleukin and tumor necrosis factor alpha (TNF-α) in patients with mild to moderate Alzheimer's disease (AD). Methods One hundred AD patients were divided into two groups in randomized controlled study, including treatment group (RNSP 1 g/d) and control group (piracetam 2.4 g/d). The treatment lasted 12 weeks. The Mini Mental State Examination (MMSE), Alzheimer' s disease Assessment Scale-cognitive subscale (ADAS-cog) and Activity of Daily Living Scale (ADLs) were taken to evaluate the efficacy. Serum levels of amyloid peptides (Aβ40 and Aβ42 ) were measured by ELISA assay. The radioimmunologic assay was used to determine the serum levels of IL-1β, IL-2, IL-6, IL-8 and TNF-α. Results The scores of MMSE, ADAS-cog and ADL significantly improved at 12 weeks after RNSP treatment (P＜0.01, 0.01, 0.05, respectively), while had no significant changes in piracetam group (P＜0.05).The levels of TNF-α, IL-1β, IL-6 and Aβ42 were significantly lower in RNSP group than in Piracetam group (P＜0.01). There was a decrease trend of the Aβ42/Aβ40 ratio at 12 weeks after RNSP treatment (P＜0. 05, P＜0.01 ). The serum Aβ42 level had strong correlations with TNF-α, IL-1 β and IL-6. There were no significant differences in Aβ40 and IL-8 between RNSP group and piracetam group. No obvious drug side effect happened on the groups. Conclusions The reductions of serum TNF-α, IL-1β and IL-6 levels after RNSP treatment may lead to decrease of Aβ42 production in AD patients. RNSP may decrease the Aβ42/Aβ40 ratio and slow down the progress of AD. It may improve the learning and memory ability in treating patients with mild to moderate AD and is well tolerated and safe.