There arc almost 40 oil or water wells in which the casing tubes cannol be pulled out in the Putaohua oil field in each of the past few years. It has hidden danger and cosls a lot to use traditional releasing tools or heavy repairing racks to solve the problem. So down well hydraulic pressure jam releasing technique has been researched with oil drain device, down well hydraulic pressure jam releasing assembly, safe joint and fishing tools; the pump truck on thc ground provides pressure for the hydraulic releasing assembly to keep safety and reduce cost. This technology can be widely used in the middie and later period of oil field development.