The invention discloses a frame-type variable capacitor and a preparation method, which belong to the technical field of micro-electromechanical system MEMS devices. The frame-type variable capacitor is characterized by consisting of three-dimensional comb-tooth-shaped drive electrodes and a three-dimensional comb-tooth-shaped adjustable capacitor and having a bi-directionally movable structure. High-frequency or radio frequency signals can be introduced by elongated and bended cantilever girders on a frame structure of the frame-type variable capacitor, so the rangeability of capacitance is low, while an absolute value is great; and the high-frequency or radio frequency signals can be introduced through a frame on the frame structure of the frame-type variable capacitor, so the rangeability of the capacitance is high, while the absolute value is small. Preferable design parameters of the variable capacitor are disclosed, and correspondingly, the preparation method is disclosed. The preparation method has the advantages of not only finishing control over a capacitance value, but also effectively improving a quality factor Q of the capacitor and the rangeability of the capacitance.