The invention provides a method for testing dynamic stiffness of a machine tool spindle based on MEMS (micro electro mechanical systems). The method comprises the following steps: firstly, arranging a force sensor and an acceleration transducer on a shaft shoulder of the machine tool spindle along the vertical direction; sticking a reflection belt on the machine tool spindle close to a grinding wheel; arranging a photoelectric sensor on the inner wall of a machine tool cabinet close to the position of the reflection belt; connecting the sensors with an industrial personal computer; and acquiring a normal displacement signal S(t) by utilizing the matrix laboratory (MATLAB) software to perform integration calculation on a signal a(t) for the acquired normal acceleration; acquiring a normal force F(Omega) and displacement S(Omega), by transforming the acquired normal force F(t) and the displacement S(t) into amplitude spectrums by performing the Fourier transform; calculating and acquiring a dynamic stiffness G(Omega) according to the normal force F(Omega) and the displacement S(Omega) by utilizing the following formula: G(Omega) is equal to F(Omega)/ S(Omega); and lastly, judging ifthe working condition of the machine tool is safe, by comparing the detected dynamic stiffness at different conditions. By using the method, the precision for testing dynamic stiffness is increased. The method provided by the invention has the advantages that the precision for testing dynamic stiffness is high and the testing cost is low.