The platinum resistance thermometer use as a standard for calibration laboratory and industrial laboratory. Two methods for calibrate the platinum resistance thermometer are fixed point cell calibration (International Temperature Scale, ITS-90) and comparison method calibration (IEC 60751). The systematic difference between ITS-90 equation and Callendar-Van Dusen(CVD) equation for platinum resistance thermometer with different values of ratio is analyzed. We calibrated many sets of platinum resistance thermometer by using comparison method. This paper is investigating the difference of two equation of calculation, the difference coefficient obtained from the ITS-90 equation and CVD equation.