Objectives: This study aimed to investigate the prevalence of insomnia and risk factors among different job categories of steel workers in China, in order to improve their quality of occupational life. Material and Methods: A cross-sectional face-to-face survey was conducted which involved 5834 steel workers from a large enterprise located in northern China, including front-line, maintenance and inspection, and other auxiliary workers. The Athens Insomnia Scale and the Job Content Questionnaire were used to assess the status of insomnia and job stress/social support, respectively. Multivariable logistic regression was used to identify factors influencing insomnia. Results: The overall prevalence of insomnia was determined at 42.0% (95% confidence interval: 40.7%–43.2%). For front-line, maintenance and inspection, and other auxiliary workers, the prevalence was 42.3%, 39.8%, and 47.9% (p = 0.001), respectively. The participants with high stress and low support, and those who had experienced ≥2 major life events in the past 12 months, compared to those with low stress and high support, and those without major events, displayed an increased risk of insomnia among all 3 job categories (the adjusted odds ratio ranged 1.56–2.38 and 1.30–1.75, respectively). The educational level, shift work, alcohol consumption, and present illness were identified as influencing factors of insomnia for 1 or 2 job categories. Conclusions: The prevalence of insomnia was the highest in the group of other auxiliary steel workers among the 3 job categories of steel workers under consideration. While the influencing factors of insomnia differed among the groups, job stress and major life events were common risk factors of insomnia among the 3 categories of steel workers. Int J Occup Med Environ Health. 2020;33(2):215–33