Abstract: Based on understanding the technical parameters, using and operating conditions of R Packer, and focuing on the working condition and difficulties encountered when releasing this packer in the S22 horizontal well of the Y Oilfield in Iran, we analyzed the amount of shear pin design for R packer and all kinds of operating conditions of releasing force calculation. to study the obscure reasons to unset this kind of packer, finally, a practical solution to unset this kind of packer is founded. Not only successfully solved the R Packer releasing problem in S22 horizontal well, but also put forward a set of optimized plan for using of R Packer in horizontal well. In the future, it provides a useful reference for this kind of packer using in the other horizontal wells in the S reservoir. Meanwhile, for the horizontal wells which had been completed in this oilfield, it provides a useful experience draw from the lessons learnt of releasing the packer for the workover operation in the future.