A sub-machine of a soda fountain with an adjustable exhaust velocity includes a main body, a water bottle connector, a housing, a taper ring, a bottom cover, a positioning seat, an air inlet assembly, an air nozzle rod, an exhaust valve and a soda bottle, and further includes a connecting seat, an exhaust knob and an exhaust key, where the connecting seat covers an upper opening of an exhaust valve cavity, an upper end of a valve rod passes through a guide hole of the connecting seat and is pivoted to the exhaust key, and a lower surface of the exhaust key is attached to a flat seat plate part; a circular body part of the connecting seat extends into an arc-shaped part, the exhaust key is nested into an exhaust key cavity, and a handle part extends out from a guide notch; the exhaust key is in sliding fit...