Changes in carbon content transform considerably the structure of alloys and affect the properties of products. Therefore, carbon influence on kinematic viscosity of Ni-Cr alloys, which are the basis of modern refractory compositions, studied. Kinematic viscosity was measured by the twisting - vibration method in the range of temperatures from 1450-1830° C in the mode of heating and subsequent cooling. Samples with carbon content of 0.03; 0.05; 0.1; 0.15; 0.2; 0.3; 0.4; 0.5; 0.7 mass % were used. Isotherms of concentrational and temperature dependences were obtained. Relative error of the temperature dependence did not exceed 0.8%, and that of the absolute value of kinematic viscosity -1.5%.