In order to study the influence of the layer of the laser cladding to the bending degree, obtain the mathematical formulation in shaft laser cladding bending and derive the empirical formula, the laser cladding test for shaft was designed. The laser cladding test had been proceeded at the same cladding area and different layer of cladding. The results of the experiment show that the shaft is bended facing the laser beam. The bending degree and the layer of laser cladding are at the direct proportion. At the same time mathematical formulation in shaft laser cladding bending has been established and the parameter which is used to measure the degree of the bending has been obtained. Empirical formula between bending degree and the layer of laser cladding has been established. The circular run-out formula along the shaft length has been derived. The calculated value and the measured value are of the goodness fit. The maximal error is 0.035mm, and the average error is 0.017mm. It illustrates that the mathematic formulation is correct and the empirical formula has high accuracy.