Based on inter-firm transaction data disclosed in the annual reports of listed companies, this paper examines the influence and action mechanism of the trade network on corporate productivity, and the influence of market access on the effect of the trade network. The results indicate that the trade network has a significant direct effect and a network effect on improving corporate productivity, and its effect is continuously enhanced with improved market access. Among them, the purchasing network deepens the division of labour under corporate vertical specialisation, the sales network expands the distribution channels of firms and forms economies of scale, and market access is conducive to reducing the fixed costs that firms must overcome in the purchasing or selling process. The trade network formed by firms with geographical proximity and industrial complementarity also has a more significant impact on improving productivity. From the perspective of broader market access, it is further found that a reduction in upstream monopolistic barriers and information barriers generated by digital transformation leads to improving the marginal effect of the trade network on corporate productivity. The conclusions of this paper provide information about the policy for constructing the modern economic system networks and the formation of a regional economic structure with complementary advantages.