Abstract: The retrievable sleeve fishing mechanism can pull a multistage ball-seat out of hole in one trip,for a full bore size inside the pipe string,with lower axial insertion loads and high load bearing.Under such circumstances,an innovative high load bearing mechanism has been developed for fishing multi-stage ball seats.Through theoretical calculation and finite element analysis,the impact of tooth root taper and loading bearing angles on axial insertion load and load bearing capacity has been analyzed,and the optimal parameters determined.Results of analyses demonstrated that the innovative heavy-duty ball-seat fishing mechanism can reduce axial insertion loads 75% compared with conventional devices.When the tooth root taper is 1:16,the axial insertion load is approximately 2 kN,while the maximum axial insertion load is as much as 500 kN.When the load loading angle is less than 90°,the axial load bearing capacities of fishing mechanism inrease as the tooth root taper increases and the axial insertion load decreases.The high load bearing fishing mechanism has been simulated to run in hole,with successful operation in one trip thus demonstrating that the fishing mechanism can effectively meet the demands of wellsite application,and provide a new way for enhancing the success rate of ball seat fishing.