An approach for analyzing 3D cardiac motion from X-ray coronary artery angiogram sequences based on non-rigid motion principles was presented. According to actual characteristics of cardiac motion which have been confirmed by medical observations, complex cardiac motion is decomposed into global rigid motion, global deformation and local motion and deformation. Parameters of all components are estimated from global to local and coarse to fine to obtain quantitative description of cardiac dynamics. Experimental results demonstrate the feasibility and efficiency of the method.