In August 2018，China's first case of African swine fever（ASF）took place in Liaoning Province，and subsequently the epidemic spread throughout the whole country. How to control and eliminate ASF has become an emergency problem to be addressed in the whole industry. In order to identify the bio-safety status of farms in Liaoning Province，and to analyze its role in prevention and control of ASF，an epidemiological investigation was carried out. For some infected farms，it was investigated that the outbreaks were caused by major risk factors including lack of loading platform of pigs，no disinfection against incoming feed，poor movement control of persons and vehicles，disordered management of disease prevention and so on；for 56 uninfected farms，it was found that the bio-safety levels of these uninfected farms were generally low，such as the lack of basic isolation facilities as well as relevant regulations and operation procedures，short of methods and experience to verify the efficiency of disinfection measures and professional technicians to evaluate the risk point of the farms，low level of“knowledge，attitude and practice”（KAP）of practitioners in farms，etc. In short，the bio-safety level of pig industry in Liaoning Province was far away from the needs of disease prevention and control，and the main causes for failed or poor prevention and control of diseases in large-scale farms were the low bio-safety level and lack of related awareness and knowledge by the farms. Therefore，a series of measures should be adopted to comprehensively improve the bio-safety level，including conducting scientific analysis and assessment for the farms through supporting by government as well as guidance and training by official technical departments，upgrading hardware，improving systems and strengthening publicity and training，etc.