Objective:To investigate the efficacy of gonadotropin releasing hormone agonist (GnRH-a) combined with a levonorgestrel-releasing intrauterine system (Mirena) in patients with adenomyosis and its effects on ovarian function, carbohydrate antigen (CA) 125, CA153 and carcino-embryonic antigen (CEA) expression.Methods:Seventy-eight patients with adenomyosis who received treatment from September 2017 to September 2020 in Shaoxing People's Hospital were included in this study. They were randomly divided into treatment and control groups ( n = 39/group). Patients in the control group were treated with a levonorgestrel-releasing intrauterine system. Patients in the treatment group were treated with GnRH-a, once per month in the first 3 months based on treatment with a levonorgestrel-releasing intrauterine system. After 6 months of treatment, changes in dysmenorrheal relief, menstrual volume, uterine volume, endometrial thickness, ovarian function, CA125, CA153 and CEA levels relative to before treatment were compared. Results:Visual analog scale score and pictorial blood assessment chart score in the treatment group were (1.36 ± 0.28) points and (38.98 ± 5.42) points, which were significantly lower than those in the control group [(1.78 ± 0.31) points, (63.42 ± 6.75) points, t = 6.27, 17.63, both P < 0.05). Uterine volume and endometrial thickness in the treatment group were (209.74 ± 15.65) cm 3 and (7.37 ± 0.57) mm, respectively, which were significantly lower than those in the control group [(278.39 ± 20.90) cm 3, (8.63 ± 0.86) mm, t = 16.45, 7.62, P < 0.05]. There were no significant differences in serum levels of luteinizing hormone, follicle stimulating hormone and estradiol between the two groups (all P > 0.05). Serum CA125, CA153 and CEA levels in the treatment group were (26.87 ± 7.21) U/L, (23.12 ± 7.38) U/mL and (5.45 ± 0.96) μg/L, respectively, which were significantly lower than those in the control group [(49.93 ± 8.97) U/L, (38.94 ± 6.21) U/mL, (8.23 ± 1.35) μg/L, t = 12.51,10.24,10.48, P < 0.05]. Conclusion:GnRH-a combined with a levonorgestrel-releasing intrauterine system (Mirena) can markedly relieve dysmenorrhea, reduce menstrual volume, uterine volume, and endometrial thickness, has no obvious effects on ovarian function, and greatly reduce the levels of CA125, CA153 and CEA. Therefore, the combined method is a safe and effective non-surgical treatment method of adenomyosis.