The short-circuit ratio (SCR) of the connected AC grid and the transmitted power of a voltage source converter based high voltage direct current (VSC-HVDC) system are subject to variations during practical operation, whereas robust stability analysis and control methods accounting for these uncertainties remain limited. The main challenge lies in guaranteeing system stability over the entire uncertainty range while maintaining computational tractability. To address this issue, this paper proposes a computationally efficient robust stability analysis and control approach for VSC-HVDC systems considering uncertainties in both the SCR and transmission power. First, a small-signal model with linear uncertain variables is established to characterize the dynamic behavior of multiple operating equilibria under SCR and power uncertainties. Based on Lyapunov stability theory, a robust state feedback control design problem is then formulated. Subsequently, a robust stability criterion and a state feedback controller synthesis method are developed using linear matrix inequalities (LMIs), enabling robust stability analysis and controller design for VSC-HVDC systems over the prescribed uncertainty range. Finally, MATLAB/Simulink simulation results demonstrate that the proposed method maintains system stability throughout the specified SCR and power operating ranges, thereby validating the effectiveness of the proposed robust control design approach.