Abstract: The present invention provides a stack machine for executing a plurality of instructions one by one. The stack machine comprises an operation folder and an execution unit. The operation folder is used for checking if one or more instructions of a predetermined number of instructions following a specific instruction in a predetermined sequence can be folded with the specific instruction according to a POC folding rule. If they are foldable, these instructions will be combined to form a new instruction. The execution unit is used for executing instructions which cannot be folded by the operation folder or new instructions generated by the operation folder one by one. The instructions are folded to enhance operation efficiency of the stack machine.