The invention discloses a reaction vessel for preparing a diameter period modulation microfilament through the electrochemistry method. A vessel body is installed on a base. A solution cavity of the vessel body is internally provided with a fixed partition plate and movable partition plates capable of being selectively installed. The solution cavity is transversely divided into at least two units with an equal proportion. The units are filled with an electrolyte at intervals according to the premodulation period requirement. The side face of one end of the vessel body is provided with first electrode holes communicated with the units, and the side face of the other end of the vessel body is correspondingly provided with second electrode holes. First electrodes are inserted in the first electrode holes. Second electrodes are inserted in the second electrode holes. A microfilament fixing groove transversely extending is formed in the vessel body, the fixed partition plate and the movable partition plates. A positioning frame is bonded with the stretch-tight microfilament through glue in the transverse direction. The positioning frame is arranged on the top of the vessel body to enable the microfilament to enter the microfilament fixing groove, and the microfilament is immersed in the electrolyte with which the unit parts are filled with. The reaction vessel is simple in structure, convenient to carry, easy to manufacture, easy and convenient to operate, convenient to detach and clean and low in cost.