The environmental issues within the transport industry need to be given priority attention. Optimizing the transport structure and promoting low-carbon transport are essential measures for achieving carbon emission reduction. However, the rail-water multimodal transport scale is currently limited. The government has to intervene in the market through incentive policies, so how to expand the revenue of carriers and enhance the volume has become a major dilemma. Our paper constructs a transport system that includes road, water, and railway, and examines the impact of incentive policies on separate stakeholders. It is discovered that incentive policies can increase the revenue of carriers and simultaneously attract more shippers to elect rail-water multimodal transport. Subsidy policy can hasten the structural transformation of inland transport, making railway transport volume rise. Unfortunately, although the dry port policy may enhance the revenue of railway carriers, it leads to an apparent decline in the revenue of road-water multimodal transport participants. However, the subsidy policy can create a win-win scenario for multiple carriers while achieving carbon emission reduction, but to the detriment of social welfare. Additionally, the paper compares the interactions between diverse incentive policies and pivotal factors such as transport time. The conclusions of our research serve strategic recommendations for maximizing carriers revenues and provide support for government decision-making.