For the service supply and demand relationship between an online store and a TPL, a decision model considering the altruism of members in an online shopping supply chain (OSSC) is constructed under the logistics service constraint. The impact of the altruism of members in the OSSC on decisions is analyzed. Firstly, the equilibrium solutions and the performance of the system are discussed in the decentralized decision scenario. Secondly, the decisions and profit of members and the system performance are discussed in the centralized decision scenario. Then, a comparative study about the two decision models revealed a conflict existing between the online store and the TPL. And the benefit conflict leads to making unbalanced decisions, which reduce the benefit of members and the performance of the whole system. Thirdly, the impacts of altruism on the decisions and benefits of all members are explored under the logistics service quality constraint. Finally, a computation example analysis is employed to further discover the law of change of decisions and performance in the two scenarios: one member has altruism attribute and both members have altruism attribute.