Abstract: The excessive or irrational use of agricultural chemicals has negatively impacted the rural environment and consumers' safety and health. It is crucial to promote the reduction of the use of agricultural chemicals urgently. Taking the example of veterinary antibiotics use in broiler farming, this paper, based on survey data on 475 contract farmers in 2018-2019, explores the relationship between veterinary antibiotics and their substitute, acidifiers, from the perspective of factor substitution. It also examines the impact of production risk perception and farming scale on this substitution relationship. The results show that: (1) Generally, there is a substitution relationship between antibiotics and their substitute. (2) The higher the farmers' perception of the production risk, the lower the possibility of substitution relationship between antibiotics and their substitutes. (3) The expansion of farming scale weakens the negative impact of production risk perception on factor substitution. It is important to assist farmers in enhancing their production risk prevention measures, reducing their perception of production risks, increasing their awareness about substitute factors, improving their technical knowledge, and enlarging farming scale.