Mastitis has been an important disease because of its common occurrence and resulting significant loss of profit. This study was conducted to investigate the risk factors related to subclinical mastitis (SCM) in large-scale farms. Eleven dairy farms with over 1,000 dairy cows were selected in Zhejiang province, China. A questionnaire on management factors potentially associated with SCM was designed and completed with the help of the managers from all the investigated farms. Aspects of management included in the questionnaire consisted of the general of farm and stalls, management of diet and water supply, cleaning of stalls, operation and hygiene of calving and milking, strategy of drying off, and detection and treatment of mastitis. The incidence rate of SCM was calculated according to the Dairy Herd Improvement (DHI) data. In this study, the SCM was defined as the SCC over 4 × 10⁴/mL milk. Correlation analysis was conducted to identify the herd management factors that were associated with an increased rate of subclinical mastitis. One-way ANOVA was used to analyze the cow factors from DHI data in SPSS 19.0. The average incidence of SCM in these farms was 17.8% in 2015. The incidence rate of SCM increased with the increasing parity and days in milk. Within a year, the incidence of SCM was highest in summer and lowest in winter. Six management factors significantly were identified to be associated with the incidence of SCM, including type of stalls (P < 0.01), milking system (P < 0.01), cleaning frequency of stall (P < 0.01), usage of milking gloves (P < 0.01), individual pen for calving (P < 0.01), and duration staying with lactating cows before calving (P < 0.01). The result of this study indicated that udder health in large dairy farms can be affected by several factors especially the hygiene of milking and calving. It warrants further investigated how mastitis caused by different management methods affects physiological changes of dairy cows.