Under the green manufacturing environment with the low-carbon emission purpose, the contradiction between idle capacity resources and shortage has become one of the critical problems in the operation of manufacturing enterprises. It is vital to realize capacity sharing and to improve the utilization rate of resources. A game model is utilized in this paper to explore the impact of Carbon-emission-trading on manufacturers' capacity sharing strategies. We consider two competitive manufacturers with sufficient capacity and insufficient capacity as the research setting and study the optimal decision problem of manufacturers' capacity sharing under consumer's preference for low-carbon products. At the same time, we verify the model by numerical simulations. The results show that the amount of capacity transferred and the transferring price per unit product are negatively correlated with the emission reduction level of the manufacturer with sufficient capacity. In contrast, the amount of capacity transferred is positively correlated with the emission reduction level of the manufacturer with insufficient capacity. When the carbon emission reduction level of the two manufacturers is within a specific range, the profits of both manufacturers will increase.