The behaviors of pig farms and households and the consistency degree of these behaviors in responding to price fluctuations are the key to the stablization of the supply and price fluctuations of pigs in China.,This paper presents an empirical study on the differences in opportunity selection behaviors of pig farms and households with different scales against price fluctuations using the contingency table and multivariate probit model based on the survey data of pig farms and households in Hebei,Liaoning and Beijing.The results showed that:1) The behaviors of pig farms and households in responding to price fluctuations are mainly changes of scale and slaughter time,supplemented by the change of production input; they tend to expand the scale,delay the slaughter time and increase production input when price rises,and tend to shrink the scale,advance the slaughter time and reduce production input when price falls.2) There are differences in opportunity selection behaviors of pig farms and households with different scales.The large-scale pig farms and households’ behavior tendency of changing the scale,slaughter time and production input against price fluctuations is slighter than that of small-scale pig farms and households,and there is a significant difference with respect to scale and production input.3) The opportunity selection behavior of pig farms and households is asymmetric when price rises or falls.The behavior tendency and its consistency degree of changing the scale among pig farms and households with different scales when price falls are greater than those when price rises,while the behavior tendency and its consistency degree of changing the slaughter time and production input are slighter when price falls than those when price rises.Therefore,promoting the pig breeding scale is helpful to smooth down the large fluctuations of pig prices,especially the cyclical fluctuations range,but the effect on cyclical fluctuations is asymmetric when price rises or falls.