Conduction transfer function (CTF) is widely used to calculate conduction heat transfer in building cooling loads and energy calculations. It can conveniently fit into any loads and energy calculation techniques to perform conduction calculations. There are three methods, Laplace transform (LP) method, state-space (SS) method and frequency-domain regression (FDR) method to calculate CTF coefficients (CTFs). The limitation of the methodology possibly results in imprecise or false CTFs. This paper desires to seek an accurate and robust calculation method through the relationship between the calculation accuracy of the three methods and material properties of building slabs. Results show that the FDR method is more accurate than the LP and SS methods. The FDR method may be a better choice to calculate the building cooling/heating loads.