The thumb key-touching is a complex spatial movement which involves many factors. Its quantitative analysis is very important for the scientific guidance of piano teaching and the quantitative evaluation of teaching effect. This paper puts forward a measurement and analysis method for the training of thumb key-touching in the early stage of piano teaching. Firstly, the Leap Motion is used to build the measurement platform to collect the motion data of key-touching. Secondly, the hand joint coordinate systems are established, and the angle parameters representing the movement of thumb key-touching are set. Then the least square method is used to obtain the motion regression equation of the thumb key-touching. Finally, according to the regression equation, the change law of joints’ angle parameters in the process of thumb key-touching is predicted. This study can provide prediction curves of thumb key-touching motion for people with different thumb lengths, provide scientific guidance for piano playing and learning effect evaluation, and provide a theoretical basis for the follow-up design of piano teaching manipulator.