The invention discloses an automatic setup adjustment and control method of a hot water constant pressure control system. The method comprises the following steps of: (1) state judgment, (2) information sampling state selection, (3) a systemic pressure judgment period, (4) a systemic pressure judgment interval, (5) a basic boundary condition of judgment, (6) a hot water constant pressure adjustment setup state, and (7) a hot water constant pressure setup pressure automatic adjustment value. The pressure of a system under a no water use condition is sampled; a system adjustment pressure setup value is optimized as 70% of a hot water pressure sampling value according to a relationship between a rotating speed and the pressure and an optimal operation pressure area (49-81% of a maximum pressure range) of the system; different water flow requirements of the system can be met; and the optimal operation area under a hot water supply condition can be met. The method avoids the situations thatthe system is in a critical constant pressure state all the time, the operation pressure is unstable, and a use effect is influenced.