Rotor dynamics design is fundamental to helicopter dynamic engineering design, and its dynamic characteristics directly affect the magnitude of hub vibrational loads, which in turn influence the aircraft's vibration levels. Addressing the issue of excessive 4th harmonic flapping loads in rotor blades, this paper employs a combination of theoretical analysis, numerical simulation, and experimental verification to systematically study the effects of integral counterweights of different materials and dimensions on rotor blade dynamic characteristics. Additionally, the aeroelastic stability of the improved blade design was analyzed to determine the optimal improvement scheme. Research results indicate that integral counterweights primarily affect the second-order flapping frequency of the blade. By increasing the integral counterweight mass to reduce the second-order flapping frequency and avoiding the 4th-order excitation frequency, the 4th harmonic flapping loads can be effectively reduced. The research conclusions provide important guidance for blade optimization design and theoretical support for reducing vibration loads in composite rotor blades.