Abstract: Under the online retail environment， the online platform channel strategy was investigated considering service quality sensitivity and channel substitution rate. The decision models of supply chain were constructed based on the fixed and variable slotting fees. With the numerical analysis， the effect of channel competition and quality sensitivity on firms’ decision making was explored， and the boundary conditions of channel selection were defined. The result showed that the channel competition improves quality investment of suppliers and platforms; furthermore， the profits increase. The increment of commissions is not always beneficial to platforms. Excessive commission rates would lead to the withdrawal of suppliers from platforms， which is not conducive to the long-term operation of platforms. For small-scale platforms， the supply chain doesn’t implement a double-channel structure when the fixed slotting fee is high. For large-scale platforms， the slotting fee has little impact on channel operations. When the operating cost of platforms is within a certain range， the dual-channel can achieve a win-win situation.

Key words: channel competition; fixed slotting fee; variable slotting fee; service quality; platforms’ channel selection