Although the large-scale grid connection of offshore wind power has led to the rapid enhancement of offshore wind power technology, the impact of Grid-Forming Wind Turbine (GFWTs) on the small signal stability of AC networks has become increasingly significant. Therefore, this paper establishes a small signal model for offshore AC networks with multiple GFWTs. Firstly, it analyzes the coupling mechanism between frequency/voltage droop control parameters and system dynamic characteristics. Secondly, based on eigenvalue analysis, it reveals the influence of droop gains on system pole distribution, indicating that excessive frequency droop gains may induce low frequency oscillation risks. Furthermore, MATLAB/Simulink simulations are carried out to verify the effectiveness of control strategies, showing that GFWTs can achieve active and reactive power decoupling control to support system stability. Finally, this study provides new research methods for control parameter tuning and stability optimization of offshore wind farms.