This paper presents the principles of space voltage pulse width modulation(SVPWM) in detail,and advances a method to exercise control on the speeds of AC motor drives based on based on flux linkage locus tracking by using software of EDA, complex programmable logic device(CPLD),chip of ALTER,and EPROM.The AC-DCAC voltage source inverter composes the main circuit of this variable frequency system and CPLD is the logic control device of the power device(IPM).The experiments prove that using this method to control inverter has the advantages of simplicity,flexibility,high efficiency and accuracy.It would be used in the system of variable frequency widely.