Objective <p>To observe the clinical efficacy of intervention with auricular point sticking at different time points in treating primary dysmenorrhea (PD) and to discover the optimal intervention timing in the treatment of PD with auricular point sticking.</p> Methods <p>Sixty PD patients were divided into a trial group and a control group using a random drawing method, with 30 cases in each group. The intervention started 7 d before the menstrual cycle began among participants in the trial group, and began on the first day of menses in the control group. The same auricular points were chosen for the two groups to administer auricular point sticking with the single-use auricular plasters, including Shenmen (TF₄), Sympathetic (AH_6a), Internal Genitals (TF₂), Endocrine (CO₁₈), Pelvis (TF₅), Subcortex (AT₄), and Kidney (CO₁₀). The intervention was performed once every other day, 3 times every menstrual cycle, 3 menstrual cycles in a row. Before and after treatment, the visual analog scale (VAS) and COX menstrual symptom scale (CMSS) scores were recorded. The total effective rate was compared between the two groups.</p> Results <p>After treatment, the VAS score and the CMSS scores of time (CMSS-T) and severity (CMSS-S) dropped significantly in both groups (<i>P</i>&lt;0.05). The trial group showed a lower VAS score than the control group after receiving the treatment for 1, 2, and 3 menstrual cycles, respectively (<i>P</i>&lt;0.05). After 3 menstrual cycles of treatment, the CMSS-T and CMSS-S scores were lower in the trial group than in the control group (<i>P</i>&lt;0.05). When the intervention finished, the total effective rate was 56.7% in the trial group, versus 20.0% in the control group; the between-group difference was statistically significant (<i>P</i>&lt;0.05).</p> Conclusion <p>Regarding the relief of PD pain, auricular point sticking performs better when introduced before menses starts compared to during menses, without causing adverse reactions.</p>