A tourism O2O supply chain where an online travel agency(OTA) collaborates with a tour operator(TO) under commission mode is considered in this paper. The optimal pricing and service decisions for the OTA and the TO are studied based on two different commission bargaining modes: The FU mode, where the offline sale price is adopted as the benchmark in commission negotiation and is the private information of the TO, and the N mode, where the online sale price is adopted as the benchmark in commission negotiation and is common knowledge. The influence of the ratio of online demand and the bargaining power on the optimal decisions and expected profits is analyzed by numerical examples. Finally, we explore how to choose a proper commission bargaining mode. The results show that in the N mode, a higher ratio of online demand may be more beneficial to the OTA. But, in the FU mode, a higher or a lower ratio of online demand may hurt the OTA. Moreover, a stronger or a weaker bargaining power may hurt the OTA. However, a higher or a lower ratio of online demand or a stronger bargaining power of the TO may be better for the TO and the whole tourism O2O supply chain. In addition, the N mode is more appropriate for the TO, the OTA, as well as the whole tourism O2O supply chain.