Based on the newly released 2023 Chinese General Social Survey data from Renmin University of China, this paper selected 869 Ecological Civilization Pilot Area participants. Study 1 explored the impact of China’s Ecological Civilization Environmental Policy (ECEP) on the spillover effects of pro-environmental behaviours (PEBs). Study 2 explored the effects of three types of environmental policy instruments on public value conflicts and PEBs. The results of Study 1 indicate that China’s ECEP has positive spillover effects on both private and public-sphere PEBs. Private-sphere PEBs mediate the relationship between ECEP and public-sphere PEBs, and ECEP has “cross sphere” spillover effects on PEBs (private-sphere PEBs to public-sphere PEBs). Public value conflict moderates the relationship between ECEP and private-sphere PEBs. In Study 2, the results showed that the highest level of public value conflict was found in the economic incentive-instrument and the lowest level of public value conflict was found in the voluntary instrument. Whether public or private-sphere PEBs, voluntary versus command-instrument can better stimulate PEBs. Based on the study’s results, it is recommended to strengthen the interpretation of environmental policies, resolve public value conflicts, and promote public-sphere PEBs by fostering private-sphere PEBs, thus promoting the spillover effect of “cross- sphere” PEBs.