Abstract: The effect of circumferential stress and thermal cycles on the hydride orientation factor（F_n） of N36 zirconium alloy tubes after hydriding has been studied, and several deviations during the test and the uncertainty of measurement for F_n has been mainly analyzed and computed. The results show that, the uncertainty among different layers in the same sample is larger than that among different samples in the same condition. A type uncertainty which results from the heat treatment, cutting, hydriding and reorientation test plays the key role, and the measurement software and personal error is relative smaller.