Non-metallic forest balls are often used to evaluate the measurement uncertainty of industrial computed tomography （CT） detection involved the material and scale of parts actually are large， which has introduced the problem of insufficient applicability and reliability. In this study， the uncertainty of industrial CT measurement was evaluated according to forest balls made of different materials， and the effects of the materials on the uncertainty were examined. First， we designed and fabricated three types of standard forest balls with different materials and calibrated them using a CMM according to the commonly used measurement range of industrial CT. Then， we performed evaluation and analysis of the measurement uncertainty for the diameter and center distance from forest balls based on industrial CT scanning and measuring. The results indicated that the influence of the material on the expanded uncertainty of diameter measurement from the forest balls was insignificant. The expanded uncertainty of measurement from the balls increased with the ball center distance， and the expanded uncertainty of non-metallic balls， including a ceramic ball and ruby ball， was essentially the same： approximately 0.003 5 mm. In comparison， that of a steel ball was 3.4 times larger， reaching 0.012 2 mm. There exists a certain system error in ball center distance measurement， however， the material influence on the standard forest balls is not evident. Center distance measurement based on forest balls of different materials has engineering value for evaluating the selection and calibration of industrial CT measurement uncertainty.