Abstract: Experimental investigation of friction coefficient and thermal load for a new viscous clutch were conducted and the friction coefficient is found to be the key specification for characterizing the viscous clutch. Based on the thoery on tribology, the lubricating regime was first verified, and an appropriate test methodology was employed to test and compute the viscous clutch. The test results was used to analyze the variation of friction coefficient when the viscous clutch operated at various relative rotating speed, input temperature and pressure. In addition, an equation which descirbed friction coefficient of viscous clutch at different relative rotating speed was established. The temperature of viscous clutch at thermal equilibrium was calculated by applying the flowing rate of lubricant and frictional power loss. Based on the result for the thermal load of viscous clutch and comparison on heat dissipation of viscous clutch, it is found that the equation to calculating the thermal load that described the frictional regime of frictional disc of viscous clutch need developing. As the axial temperature on frictional set is unbalanced, the flowing rate of lubricant should be optimized based on its configuration and a proposal for the optimization should be made accordingly.