Objective To evaluate the effect of horticultural therapy (HT) on cognitive function and quality of life in elderly patients with mild-to-moderate Alzheimer disease (AD). Methods A total of 130 in- and out-patients with mild-to-moderate AD in our hospital from December 2014 to December 2016 were recruited and randomly divided into HT group and control group, with 65 cases in each group. The patients of control group was given conventional therapy, oral administration of donepezil combined with nicergoline, while those in the HT group received HT on the basis of conventional treatment. Mini-mental state examination (MMSE) and generic quality of life inventory-74(GQOL-74) were used to evaluate the patients before treatment and in 3 and 6 months after the treatment. SPSS statistics 19.0 was used for data processing. According to the data types, the independent sample Student’[KG-*3]s t test or the Chi-square test were used for the intergroup comparison, and repeated measurement of variance analysis was used for comparison between groups. Results The total score of MMSE in the control group was increased significantly after 6 months compared with the score before treatment (P<0.05). In the HT group, the scores of language function, remembrance, recall and the total MMSE score were significantly increased after 3 and 6 months’ treatment compared with those before treatment (P<0.05). Compared with the scores of control group in 3 and 6 months after treatment, the scores of language function [(6.89±1.46) vs (5.21±2.36), (8.82±1.22) vs (6.80±1.49)], remembrance [(3.47±0.48) vs (2.04±0.65), (4.02±1.06) vs (2.92±0.86)], recall[(2.73±0.59) vs (1.03±0.78), (3.24±0.72) vs (2.24±0.92)]and the total score of MMSE [(20.82±1.35) vs (16.78±1.46), (24.02±2.20) vs (18.92±2.15)] was significantly increased in the HT group (P<0.05). Social function, psychological function, physical function and total score of GQOL-74 were significantly improved in the HT group after 3 and 6 months than before treatment (P<0.05). Compared with the control group, the social function score in HT group was improved significantly after 3 months treatment [(67.02±7.51) vs (63.28±9.52), P<0.05], while after 6 months treatment, social function [(69.33±6.94) vs (64.19±11.25)], psychological function [(57.12±13.07) vs (52.12±9.08)], physical function [(72.38±8.32) vs (66.85±10.08)] and the total score of GQOL-74 [(68.46±9.34) vs (63.95±10.11)] were significantly increased (P<0.05). Conclusion HT can effectively improve the cognitive function and quality of life in the patients with mild-to-moderate AD, and it has an importance to be popularized clinically.