The objectives of this epidemiological study were to evaluate the prevalence of farmer's lung disease (FLD) and to explore the potential risk factors for FLD among Chinese greenhouse farmers. A total of 835 plastic film greenhouses, including 5,880 active farmers who engaged in crop cultivation or poultry farming, were randomly selected from the rural regions of Northeastern China. These farmers participated in the study by answering a medical questionnaire. 5,420 greenhouse farmers accepted and answered questionnaires in full (response rate, 92.18 %). Prevalence of FLD among these farmers was 5.7 % (308/5,420). Besides, a number of classic risk factors for FLD were identified, such as years of age, shorter time interval for re-entry greenhouse, ventilation frequency of greenhouse more than once per 4 h, the area of greenhouses greater than 30 m(2) but without a ventilation facility, ventilation duration less than 30 min every time, greenhouse with height less than 1.8 m, greenhouse with humidity greater than 65 %, frequent exposure to moldy materials in greenhouse, living inside greenhouse, and et al. FLD is and will continue to be a real health problem for Chinese farmers. If these preventive measures are implemented, the prevalence of FLD in Chinese greenhouse farmers might be greatly reduced.