With the advent of the digital era, data elements have become the core driving force to promote the transformation and upgrading of the green economy. As a key measure for the development of data element markets, data trading platforms play an important role in enhancing green total factor productivity (GTFP) and realizing sustainable development. However, from the perspective of data factor marketization, there have been few in-depth explorations in the academic field regarding the channels and mechanisms through which data elements affect GTFP. This paper regards the successive establishment of data trading platforms in 2014 as a quasi-natural experiment. It selects data from 272 prefecture-level cities over the period from 2010 to 2020 and investigates whether the construction of data trading platforms has an upgrading effect on GTFP by using the time-varying difference-in-differences model. The study finds that the construction of data trading platforms can significantly enhance GTFP. This conclusion remains robust after a series of tests, including parallel trend tests, placebo tests, and propensity score matching tests. Specifically, the construction of data trading platforms can promote GTFP through three channels: the green innovation effect, the green financial effect, and the digital industry agglomeration effect. The credit environment and the level of digital economy development play a reinforcing role in the process of promoting GTFP improvement through the construction of data trading platforms. Further analysis reveals that the effect of data trading platform construction on GTFP enhancement is heterogeneous across geography, resource endowment, and environmental protection attention. The construction of data trading platforms has a significant effect on GTFP enhancement in the eastern region, non-resource cities, and key cities for environmental protection. Possible marginal contributions of this paper compared to the existing literature are as follows: First, from the perspective of data factor marketization, the construction of a data trading platform is regarded as a quasi-natural experiment. This provides an in-depth study of the impact of data elements on GTFP at the city level and expands the previous literature on the influencing factors of GTFP. Second, this paper analyzes the theoretical mechanisms through which the construction of a data trading platform affects GTFP and empirically tests the channels of the green innovation effect, green financial effect, and digital industry agglomeration effect, as well as the existence of the digital economy development and credit environment adjustment mechanisms. Based on the heterogeneity of GTFP, this paper further investigates the impact of data trading platform construction on urban GTFP across different regions, resource endowments, and degrees of environmental protection. To a certain extent, this study reveals the internal logic between the construction of data trading platforms and GTFP, expands research in the field of green economic development, deepens the understanding of the value of data elements, and provides a useful reference and support for the construction of data trading platforms, green economic development, and relevant government policy formulation.