Abstract: Because of axis deflection and asymmetric load distribution of the rotary kiln, the cracking of supporting shaft occurs frequently. By the analysis of the shaft of supporting wheel, a formula for equivalent stress amplitude is derived in this paper. A practical example shows that the fatigue strength of supporting shaft is mainly affected by the corresponding load. The equivalent stress varies linearly with the corresponding load. Based on the relation between the distribution of supporting system load and operating axis deviation, a linear formula for supporting system fatigue strength and axis deviation is gained. Some helpful conclusions are drawn for further study.