For a Francis turbine, the movable guide vane is mainly used to regulate the flow rate and circulation, the relative positions of guide vane, stay vane and the runner directly affect the internal flow of water guiding mechanism and runner, which play an important role in the safe, stable and efficient operation of the turbine. The commercial software ANSYS CFX 160 was used to calculate the threedimensional steady flow in the full flow channel of a hydraulic turbine model machine. Five guide vane distribution circle diameter schemes were proposed to be analyzed, aiming at obtaining the energy characteristics and internal flow fields of the turbine under different schemes. Then the best position of the active vane placement was determined, and the results showed that by appropriately increasing the circular diameter of the guide vane distribution, the lowpressure area at the suction surface of the blade could be improved, the maximum flow velocity around guide vanes could also be reduced, the flow angle at the inlet of the runner was more reasonable, and the hydraulic losses of the guide mechanism and the runner were decreased, and the turbine operating efficiency was improved. At low flow rates, D0/D1(guide vane distribution circle diameter/runner diameter) was increased by 0.031, and the turbine corresponding efficiency was increased by 5.28 percentage points, at designing flow rate or high ones, the influence of change of guide vane distribution on the turbine efficiency was smaller than that at low flow rates. Compared with the different circle diameter schemes of guide vane, the difference between the highest efficiency and the lowest efficiency were 0.17% under the design condition and 0.48% at the high flow one, respectively. Therefore, changing the distribution circle diameter of the guide vane within a certain range had the engineering practicability in the capacityincreasing projects of the waterpower station units, which can be applied in optimizing the Francis turbine.