In the process of the micro-pile reinforced slope engineering, the flexural bearing capacity of piles is an important indicator for the evaluation of the stability of the slope. Therefore, the calculation method of equivalent stiffness of micro-piles has thus been proposed. Based on the formula of flexural capacity of concrete-filled steel tubular piles and taking into consideration such factors as the influence of cement mortar in the compression area, a derivation of calculation formula can be achieved of the flexural capacity of two micro-piles with different reinforced sections. Finally, the stress state and distribution of micro-piles in the process of loading can be obtained based on three-point numerical tests, thus obtaining the load deflection curves of micro-piles, which verifies the calculation formula of bending capacity of micro-piles. The results show that the numerical test results are close to the results calculated by the formula of flexural bearing capacity, which are relatively safe and meets the engineering requirements.