The surface tension and specific heat of superheated and undercooled Ni-18.8 at.% Si alloy melt have been measured by the oscillating drop method and the drop calorimetry technique in combination with electromagnetic levitation, respectively. The surface tension follows a linear relationship with temperature within the range of 1370-2100 K. The surface tension at the melting temperature and the temperature coefficient are determined to be 1.796 N/m and -3.858 x 10(-4) N/m/K, respectively. The specific heat is determined to be 40.80 +/- 1.435 J/mol/K over the temperature range 1296-2000 K. The maximum undercooling of 178 K is achieved in the experiments. Based on the measured data of surface tension and specific heat, the viscosity, solute diffusion coefficient, density and thermal diffusivity of liquid Ni-18.8 at.% Si alloy are calculated.