Third-party integrators attempt to aggregate the services of multiple independent ride-sourcing platforms, acting as a platform of platforms, e.g., Amap and Baidu Maps. They provide a new business mode for ride-sourcing market, which benefits consumers who need ride-sourcing services. We consider there exists an integration platform composed of multiple ride-sourcing platforms (indexed by I), and an independently operated platform (indexed by 0) in the market. Platform 0 has three strategies: 1) operating independently; 2) joining the existing integration platform I; 3) setting up a new integration platform to integrate other little ride-sourcing platforms. This paper studies platform 0’s optimal integration strategy by considering the impact of the competition network effect among passengers on consumers’ total waiting costs. We find that the competition effect among passengers, the user traveling cost, and the platform's commission rate are significant factors affecting the optimal integration strategy of platform 0. Specifically, when these factors make the price of platform 0 higher than that of platform I, platform 0 should not continue to maintain independent operation. Besides when the commission rate of platform I is higher than the threshold, platform 0 should choose to set up a new platform integrator by itself. This paper bridges the gap of the existing research on ride-sourcing platform integrators and provides some theoretical support for the operation of ride-sourcing platforms.