The study investigated the effect of the Chinese herbal preparation Xuefu Zhuyu (XFZY) oral liquid on primary dysmenorrhea (PD) in women aged 18–35 years in a multicenter, double-blind, randomized, placebo-controlled trial. Of the 256 participants, 129 received XFZY and 127 received placebo for 3 months, with the primary outcome being change in pain intensity as measured by the VAS scale. There was no significant difference in the primary outcome between groups (adjusted mean difference: -0.18, 95% CI: -0.67 to 0.31, P = 0.463). However, the XFZY group had significantly lower rates of pain medication use (9.2% lower during treatment, 10.1% lower overall; P < 0.05) and consumed fewer of these medications ( P < 0.05). Other secondary outcomes, such as quality of life or duration of pain, did not differ significantly between groups. The incidence of adverse effects was similar in both groups. The study did not show an improvement in pain intensity, but XFZY reduced the need for analgesics and demonstrated good safety.