Background: Exposure to ambient fine and respirable particulate matter is associated with poor sperm quality, but evidence for particulate matter with an aerodynamic diameter ≤ 1 μm (PM1) is scarce. We aimed to estimate the association between PM1 exposure and sperm concentration, sperm count, sperm total motility, and sperm progressive motility in Chinese men. Methods: We conducted a cross-sectional study of 33,221 men attending an infertility clinic in Hubei, China, between 2014 and 2020. Daily concentrations of PM1 data were estimated from a validated spatiotemporal artificial intelligence model. We used multivariate linear regression to estimate the association between PM1 exposure and sperm parameters during the spermatogenesis period after adjusting for age, body mass index (BMI), education, ever having fathered a child, and season of semen collection. In addition, we performed stratified analysis to assess whether the association was varied by age, BMI, and educational attainment. Results: A total of 27,854 participants were included in the final analysis. An interquartile range (17.2 μg/m3 ) increase in PM1 during the entire period of semen development was associated with declined semen concentration [-4.39% (95% CI: − 7.67%, − 1.12%)] and sperm count [–23.56% (95% CI: − 28.95%, − 18.18%)], reduced total motility [-0.86% (95% CI: − 1.66%, − 0.06%)] and progressive motility [-2.22% (95% CI: − 3.00%, − 1.43%)]. The associations were homogeneous across subgroups defined by age and education, but were more pronounced among men with underweight for sperm concentration and sperm count. We identified a critical exposure window of 0–9 lag days, 10–14 lag days, and 70–90 lag days before semen collection for sperm count and progressive motility. Conclusions: Among men attending an infertility clinic in China, exposure to PM1 was associated with poor semen quality, especially during the 70–90 days before ejaculation. These results suggest that exposure to PM1 might be a novel risk factor for impaired semen quality.