Abstract: First, the expressions of axial force and bending moment for the rotating composite beams were deduced based on the constitutive relations of composites under hygrothermal environment. The influences of temperature and humidity on axial force and bending moment were analyzed. Then, the d'Alembert principle was employed to establish the lead-lag vibration governing equation for the rotating composite beams. The temperature and humidity effects on the stiffness of rotating composite beams were investigated after solving the equation by Galerkin method. Finally, the effects of hygrothermal environment on lead-lag vibration dynamic characteristics of rotating composite beams were analyzed by numerical simulation. The results show that hygrothermal environment affects lead-lag vibration frequency and modal of rotating composites beams conspicuously. Lead-lag vibration frequency decreases when the hygrothermal environment exacerbates. The effect of thermal expansion on lead-lag vibration frequency is more obvious than that of material properties variations. The combined effect of hygrothermal environment and rotating result in the obvious locational excursion of modal nodes.