This research has developed an algorithm that minimizes exposure dose of disassembly sequence of equipment in a nuclear power plant in order to improve safety and efficiency of the decommissioning process. Time complexity to obtain the optimum disassembly sequence is known as a NP complete problem. A disassembly state graph is automatically constructed from 3D CAD models of the disassembly object. Size of the disassembly state graph is reduced by eliminating the higher exposure dose disassembly process when it is assigned to a node of the disassembly state graph. On the size reduced disassembly state graph, disassembly sequence with the smallest exposure dose is explored. The exposure dose rate in each disassembly process is estimated by exposed surface area of the components having the dose rates. The dose rates of the components are integrated by time of the disassembly process in the exploring disassembly sequence.