Rodents are important reservoirs of zoonotic pathogens, and the Capillaria hepatica they carry pose a potential threat to public health in grassland ecosystems. Climate-driven changes in precipitation show complex effects on disease ecology, particularly in steppe grasslands where extreme weather events are becoming increasingly frequent. Here, to investigate the effects of precipitation patterns on the epidemic dynamics of C. hepatica in host populations, we conducted a 7-year manipulation experiment in twelve 0.48-ha field enclosures in semiarid steppe grassland. We found that rainfall increases in the early growing season intensified the infection rate and infection intensity of the parasite. Structural equation model demonstrated that additional precipitation indirectly affected epidemic dynamics by changing population parameters including body weight and population size. On the other hand, C. hepatica in the enclosure also exhibited obvious male-biased parasitic characteristics, which were not observed in the wild population. In brief, our results provide experimental evidence for the impacts of rainfall patterns on parasite epidemiological dynamics at population level and highlight the importance of early rainfall increase on the parasite transmission in the semiarid grassland.