The invention discloses a partial pressure point determination method of two sets of pipe network water injecting systems, and belongs to the technical field of oil field water injection. Technical parameters of the water injecting systems and single wells within the jurisdiction are acquired; mathematical models of operation efficiency and partial pressure points are built; relation functions of operation efficiency with pressure and water quantity are obtained through the mathematical models; an iteration simulation method is set for calculating a partial pressure point calculation range and a calculation step length; as a partial pressure point is determined, the numerical value of the partial pressure point is inevitably between 0 and a highest dry pressure of the water injecting systems, and the partial pressure point calculation range is determined as Pf.y.d (0, Pg. g); meanwhile, in order to guarantee the calculation precision of the partial pressure point, the calculation step length is determined as 0.1 MPa; all parameter values are substituted in the mathematical models for iteration calculation to obtain an eta-efficiency solution set, and an eta-efficiency solution set data curve is drawn based on the solution set; the curve is a parabola curve; the vertex of the parabola is the highest point of pipe network efficiency; and the numerical value of a corresponding pressure point is the derived optimal partial pressure point.