Based on the variational principles and the work, aerodynamical calculation was presented for the blade-to-blade flow on S_1 stream sheet of centrifugal compressor (Type: 11GJ and 110J). The calculation shows that the efficiency of Type 110J (74%) is greater than that of Type 11GJ (72%). The result is fully in agreement with that of the experiment performed by the Wusih Power Machine Plant.