Variable-pitch inducers can be fixed before impellers to lower the NPSHr of pumps efficiently. But their design method is still in groping stage. Starting with analyzing the variation regularities of pitch for variable-pitch inducers, considered that no cavitation in its inlet and the head could satisfy centrifugal impeller's intake energy, the computational method of the basic-structure parameters of an inducer has been deduced. Moreover, satisfactory cavitation performances were achieved by using the proposed method to design the variable-pitch inducer.