Functional constipation (FC) is a chronic disease that significantly affects the life quality of patients. Acupuncture has been used for the treatment of FC for many years, but its effectiveness has not been scientifically assessed. The present study aimed to evaluate the efficacy of electro-acupuncture (EA) in relieving the symptoms, mental states and quality of life (QOL) of FC patients. A total of 96 FC patients were randomly allocated into EA, mosapride & sham EA group (MS) and mosapride control group (MC). In the EA group, patients were treated with 16 sessions of needling at Quchi (LI11) and Shangjuxu (ST37) bilaterally, 5 times a week in the first 2 weeks, and 3 times a week in the last 2 weeks. In the MC group, patients were treated with 5 mg mosapride citrate three times a day for 4 weeks. In the MS group, patients underwent sham EA and the same mosapride citrate treatment as in the MC group. The primary outcome was the number of weekly spontaneous bowel movements (SBMs). The secondary outcomes included stool consistency, intensity of defecating difficulty, 36-Item Short-Form Health Survey (SF-36), Self-rating Anxiety Scale (SAS), Self-rating Depression Scale (SDS), and the validated Patient Assessment of Constipation-Quality of Life (PAC-QOL). The results showed that as compared with the baseline, EA significantly improved the weekly SBMs, stool consistency and intensity of defecating difficulty (P<0.05). It also partly ameliorated the PAC-QOL, SF-36, SDS and SAS scores when compared with MC or MS group (P<0.05). However, no significant difference was observed between MS and MC groups in bowel function outcomes and QOL scores. It was concluded that EA could effectively improve bowel function, mental states and QOL of FC patients.