In order to reveal the pulsation law of pressure and flow rate for a new kind of non-circular gear pump on the basis of oval gears used as working components， the true three-dimension unsteady numerical simulation of external non-circular gear pump is successfully implemented by the use of the dynamic mesh technique in the software Fluent． The pressure and flow fluctuations of oval gear pump are captured，and the flow field distribution， the law of pressure differences at mesh points and the law of outlet flow rate are obtained． Unexpectedly，the flow and pressure fluctuations of oval gear pump are larger than those of normal gear pumps although the flow increases as we wish，which can hardly meet the practical needs． In order to reduce the flow fluctuations， two identical pumps are used to compose a parallel gear pump in structure which makes the fluctuations of two pump outputs compensate

each other． Another simulation of the parallel gear pump proves that the flow fluctuation has a decrease of 56 percent，compared with the mono-bloc unit oval gear pump． Therefore， the new parallel gear pump is much more worthy in practical application．