The high penetration of renewable energy sources interfaced throush power electronic converters often leads to small-signal stability issues. Therefore, it is critical to quantify the impact of control parameters in multiple grid-connected converters on the small-signal stability of power system. To this end, this paper derives the small-signal stability criterion and provides the quantitative analysis of parameter sensitivity for multiple grid-connected converter systems (MGCCSs) based on extended Gershgorin theorem, thereby clarifying the influence of control parameters on the small-signal stability and providing the foundation for adaptive control. Crucially, leveraging this sensitivity analysis, we propose an adaptive control strategy involving targeted parameter adjustment for the identified weak links to ensure that the system operates with a specified stability margin. Both theoretical analysis and simulation prove the effectiveness of the proposed adaptive control strategy in the improving the small-signal stability of MGCCSs. Importantly, the proposed adaptive control strategy also demonstrates the significant potential for online application to adaptively compensate the small-signal stability margin in real time.