This paper deals with the determination of the thermal conductivity of liquid-phase phase change materials (PCMs) near the melting point by studying the evolution process of the solid-liquid interface. A theoretical model was proposed which enables the thermal conductivity to be determined from the displacement characteristics of interface during a melting process. Experiments were performed using a well-designed testing system for two kinds of inorganic PCMs, and the experimental results agreed with the literature values within a range of 6%. The sources of measurement error were studied from the temporal variation characteristics of the experimental results. It is found that the non-ideal boundary conditions of the testing system and the onset of the natural convection were the major causes of the measurement error. To improve the accuracy of the experimental results, numerical techniques were utilized to simulate the melting process of the experiments. The calibrated values of the thermal conductivity were iteratively obtained from the comparisons of interface movement curves between the experiments and simulations, and the discrepancies between the calibrated results and the reference values were limited to 3%. (C) 2017 Elsevier Ltd. All rights reserved.