Environmental regulation is to restrict pollutes emission of economic main bodies for protecting and improving environment, among which formal environmental regulation embodies the activities of environment protection by governments, however, informal environmental regulation reflects the self-consciousness of environment protection by the inhabitants. Formal and informal environmental regulation is consistent in their aim but they are different in regulation main body and regulation method so that their pollutes emission reduction effect has both synergy and heterogeneity. At the same, because the regulation environment of economic development stage, regional industrial structure, inhabitant income level and so on is different and because the time for the regulation implementation is different, the pollutes emission reduction effect of formal and informal environmental regulation demonstrates obvious spatial-temporal heterogeneity. The analysis by taking the relevant data of the 14 prefectures in Xinjiang from 2007 to 2017 shows that formal environmental regulation has significant carbon emission reduction effect as a whole, although informal environmental regulation has insignificant effect on carbon emission reduction, it can intensify the carbon emission reduction effect of formal environmental regulation. From the perspective of time heterogeneity, the carbon emission reduction effect of formal environmental regulation and its synergy effect with informal environmental regulation are stronger during 2012-2017 than that during 2007-2011. From the perspective of spatial heterogeneity, formal regulation has significant carbon emission reduction effect in north Xinjiang area but has insignificant effect in south Xinjiang area. Further analysis finds that, in Xinjiang, with the improving of economic development, the correlation between both formal and informal environmental regulation and carbon emission intensity become negative from positive, and the change of formal environmental regulation goes ahead of informal environmental regulation. Generally, in the process of carbon emission, the action of formal environmental regulation is stronger than that of informal environmental regulation and takes action earlier, in the area with more pollutes emission, the effect of environmental regulation on carbon emission reduction is stronger. Thus, on the one hand, governments should further uphold the enthusiasm on environment protection, improve the direction and efficiency of formal environmental regulation and raise the regulation intensity in the latecomer areas, on the other hand, we should continuously raise the income and quality of Chinese residents, boost social organization development, increase the consciousness of environment protection of the residents, so as to bring into fully play the carbon emission reduction effect of informal environmental regulation and its synergy effect with formal environmental regulation.