To study the efficacy of electro-acupuncture for the relief of labor pain, and to build a better understanding of how electro-acupuncture might influence the neuroendocrine system, 36 primiparas were randomly divided into an electro-acupuncture group and a control group. Assessments of pain intensity and degree of relaxation during labor were analyzed. The differences between the electro-acupuncture group and the control group on the concentration of beta-endorphin (beta-EP) and 5-hydroxytryptamine (5-HT) in the peripheral blood were compared. The electro-acupuncture group was found to exhibit a lower pain intensity and a better degree of relaxation than the control group (p = 0.018; p = 0.031). There existed a significant difference in the concentration of beta-EP and 5-HT in the peripheral blood between the two groups at the end of the first stage (p = 0.037; p = 0.030). Electro-acupuncture was found to be an effective alternative or complementary therapy in the relief of pain during labor. The benefit of electro-acupuncture for relieving labor pain may be based on the mechanism of producing a synergism of the central nervous system (CNS) with a direct impact on the uterus through increasing the release of beta-EP and 5-HT into the peripheral blood.