Elastic scattering properties of the ultracold interaction for the triplet state of 39K have been studied using a potential composed of short-range and long-range terms, where the long-range term has a multiplier: "cutoff function". For governing the decrease of the cutoff function, the "cutoff radius" has been adjusted by comparing it to experimental energy values. The scattering properties have then been found using the solutions of the radial equation for two methods, the WKB and the Numerov method. The obtained results have been compared in detail with the experimental and other theoretical results. © 2005 the Physical Society of the Republic of China.