Abstract: A method for assembling a front cover to a bush in a pneumatic tool is to perform a leading operation first in which a blank of front cover is worked with hydraulic forming and being roughly machined and a blank of bush is roughly machined and heat-treated and the then the front cover is joined tightly to the bush before a process of surface treatment being conducted to obtain a finished piece. Hence, in addition to work efficiency and precision of the integral structure of the pneumatic tool being enhanced, it is capable of extending life span and lowering production cost of the pneumatic tool substantively.