The present invention relates to a three-piece wrench comprising: a wrench body with a working head and a shaft, the working head is located at a front end of the shaft, the shaft has a length; a first extension rod with a length; and a second extension rod with a length; the lengths of the first extension rod and the second extension rod are greater than the length of the shaft; combination of the wrench body, the first extension rod and the second extension rod provides various usage lengths of the wrench, so that different connection types can be used to form required lengths according to requirements.