Errors in measurement of temperature have a significant negative impact on the thermal conductivity measurement. This paper analyses the causes of temperature error and why a small temperature error could often cause a huge error in thermal conductivity instrument. Since traditional methods often involve complex circuits or formulas, here we introduce a convenient and efficient method to improve temperature measurement accuracy, which by effectively combination of the table consulting and a new simple interpolation method introduced in this paper. It is implemented in the LabVIEW environment and experimental results show the accuracy of the instrument has been greatly improved.