Environmental regulations are changing the size of employment as well as the structure of employment.To assess this impact, this paper identifies labour allocation efficiency in the classical economic growth equation and uses exponential decomposition to decompose labour allocation efficiency into labour input efficiency and labour allocation structural efficiency to measure the impact of employment size and employment structure on labour allocation efficiency, respectively. Based on the multi-temporal DID, this paper analyses the causal relationship and long-term impact of the carbon emissions trading pilot on labor allocation efficiency through a series of robustness tests such as event study method, counterfactual framework, PSM-DID, spatial-DID and placebo test, and draws the following conclusions: 1) The implementation of the carbon emissions trading pilot has a positive impact on labor allocation efficiency in the pilot region. 2) The impact of the pilot on labour allocation efficiency shows spatial and temporal heterogeneity. That is, on the one hand, this impact gradually increases over time. On the other hand, the efficiency of labour allocation varies across regions in China. In the eastern pilot regions, labour allocation efficiency decreased by an average of 3.67%, including a 2.05% decrease in structural labour allocation efficiency; in the central pilot regions, labour allocation efficiency increased by an average of 3.98%, including a 6.80% increase in labour allocation efficiency; in the western regions, labour allocation efficiency increased by an average of 3.39%, including a 1.09% decrease in structural labour allocation efficiency 3) There is a spatial spillover effect of the pilot policy on carbon emissions trading. In other words, the policy pushes labour from the periphery to the pilot area, thus reducing the efficiency of labour allocation in the periphery.