Abstract: Interest coordination is the key to the successful cooperation of the two parties involved in the cloud accounting service supply chain in the context of buying out copyright. The research focus on the option contract coordination at the two levels of supply chains consisting of one cloud accounting product provider and one cloud accounting service supplier. In the research, by using initial ordered quantity and service rent price of the service supplier as the decision viable, an option contract model is built to show the correlation between demand and service rent price. The research shows that the option contract alone cannot realize the coordination of cloud accounting service supply chains, but on the basis of the option contract, the united option which allows the service supplier to return the earnings in part to the product provider helps better coordinate the supply chains. The research results can be used as the basis to make decisions on the coordination of supply chains in the context of buying out copyright. The effectiveness and rationality are verified by analyzing computation examples.

Key words: option contract, cloud accounting, service supply chain, coordination