This paper presents the differences in thermodynamic properties of refrigerants in different spatial conformation, showing the superiority of molecular simulation in predicting thermodynamic properties of fluids. And molecular simulation was modified to improve prediction accuracy of thermodynamic properties of fluids at high temperature and pressure. Meanwhile, a new high temperature heat pump refrigerant mixture named NBY-1 was proposed, and its thermodynamic properties were estimated with the modified molecular simulation. Then the experiment investigation was carried out and showed the good cycle performance of NBY-1 as the refrigerant. The experimental results indicated that high temperature heat pump using NBY-1 could supply high temperature water of 130 degrees C with the highest coefficient of performance of 2.74 and the condensing pressure of 2.55 MPa, when the temperature lift was 50 degrees C. Moreover, the experiment also demonstrated the high accuracy with molecular simulation in predicting thermodynamic properties of NBY-1 in the two phase region, and the average relative deviation of condensing pressure between predicted results and experimental results was 2.59% with the highest value of 3.89%.