The present invention relates to the field of breathing machine equipment. An integral oxygen mixing channel of an oxygen mixing valve of a breathing machine of the present invention comprises an adjustable piston sleeve (1), an adjustable piston (2) and a valve body (7), the adjustable piston sleeve (1) being connected to one end of the adjustable piston (2) via an internal thread, and then being connected to the valve body (7) via an external thread, wherein the other end of the adjustable piston (2) penetrates through the valve body (7)； and both ends of the adjustable piston (2) are coaxially provided with a pair of seal ring grooves (14), respectively, the seal ring grooves (14) are placed with seal rings (3) therein, and an area of the adjustable piston (2) between the two seal rings (3) is designed into a hollow cylindrical shape to form an oxygen mixing channel (12). This structure can ensure a controllability of adjustment of the concentration of the mixed oxygen in terms of a mechanism, greatly simplifying a debugging process of a production line, that is, the debugging may be accomplished by the adjustment at one end, therefore greatly reducing the difficulty in debugging and improving the production efficiency.
