Multi-string locking and releasing mechanism for downhole tool

The utility model relates to a multi-stage locking and releasing mechanism for downhole tools, which can be matched with a packer, a tubing anchor, etc. The mechanism is composed of a protective tube, a press locking tube, a releasing tube, a central tube, a lock ring and shear pins, wherein, the upper end of the protective tube is connected with the lower end of the press locking tube by using threads; the releasing tube is arranged in the releasing tube; the center pipe is arranged in the lower half part of the releasing tube; the lock ring is positioned in a cavity surrounded by the lower end of the press locking tube and the protective tube; inner sawteeth of the lock ring and outer sawteeth of the central tube are arranged in a matched way. The mechanism has double functions of locking and releasing of the downhole tools, and is especially suitable for multi-stage locking and releasing. The utility model has the advantages of simple structure, small axial dimension, high safety, low cost and convenient operation.