Farmers perceptions of climate risk reflect their subjective probability weighting bias, which are the prerequisite for their adaptation decisions and thus shape their actions. As an adaptation strategy, farmers prioritized the technological measures of chemical input as the most simple and convenient for climate risks. However, this is little evidence of empirical work on the mechanism between farmers perceptions and chemical use behavior. Based on cross-sectional data from a survey of farmers in China, this study develops a theoretical framework that considers adaptation decisions of heterogonous farmers within a perception-decision-action (PDA) analytical framework, and further estimates the effects of farmers perceptions on chemical use behavior by utilizing endogenous switching regression model. The results indicate that under ceteris paribus, the key variables perception of climate risk of farmers have significant effect on their claim of increase in the quantity of chemical use. We find evidence of crowding-in of farmers perceptions on chemical use?which in turn will have negative effect on environment and food quality. The paper concludes by offering some policy implications for the presented results. Acknowledgement : Acknowledgements We are grateful for support from the Key Project of National Natural Science Foundation of China (No.71633002), the National Natural Science Foundation of China (No. 71273234), the Key project of the Ministry of Education (No.16JJD63007), The Key Project of National Social Science Foundation (No. 13AZD079), and The Key Soft Science Project of Science Technology Department of Zhejiang Province (No. 2017C35G2100255).