A system for realizing rotor variable frequency speed control asynchronously and simultaneously by driving four motors via one inverter, comprised of a motor group, a rectifier group, a chopper group, an isolator group, a current limiter group, a power capacitor group, an inverter, a speed feedback voltage detector and a current feedback voltage detector, the respective rotors of four motors M 1, M 2, M 3 and M 4 in said motor group are respectively connected to the respective corresponding input terminals of four rectifiers Z 1, Z 2, Z 3 and Z 4 in rectifier group in turn; the respective emitters E of four choppers IGBT 1, IGBT 2, IGBT 3 and IGBT 4 in said chopper group are respectively connected to the anodes of the respective corresponding three rectifier diodes of four rectifiers Z 1, Z 2, Z 3 and Z 4 in said rectifier group at point D, in turn; said inverter being a full-bridge inverter, which comprises six silicon controlled invertors, i.e., KP 1, KP 2, KP 3, KP 4, KP 5, and KP 6, each having a respective inductor L1, L2, L3, L4, L5 and L6 in series, and the three connection points of the output terminals KP 1 and KP 4, KP 2 and KP 5, KP 3 and KP 6 being respectively connectable to the ends A, B and C of a three-phase industrial AC power supply in turn, and then connected to the respective stators of the four motors M 1, M 2, M 3 and M 4 in said motor group, through said inductors L1, L2, L3, L4, L5 and L6, characterized in that: said isolator group comprises eight isolators D 1, D 2, D 3, D 4, D 5, D 6, D 7, and D 8, wherein D 1 and D 5, D 2 and D 6, D 3 and D 7, D 4 and D 8 are respectively connected in series; the respective anodes of isolators D 1, D 2, D 3 and D 4 are respectively connected to the output terminals of respective corresponding resistors R 7, R 8, R 9 and R10 in turn, and the collectors C of choppers IGBT 1, IGBT 2, IGBT 3 and IGBT 4, in turn; the other sides of the resistors being connected to the cathodes of the rectifiers Z1, Z2, Z3 and Z4, in turn; and the cathodes of isolators D 5 and D 6 are connected to the input terminal of current limiting inductor L 7 in said current limiter group, while the cathodes of isolator D 7 and D 8 are connected to the input terminal of current limiting inductor L 8 in said current limiter group, the connection points of isolators D 1 and D 5, D 2 and D 6, D 3 and D 7, D 4 and D 8 connected in series in said isolator group are respectively connected to the respective one end of capacitors C 13, C 14, C 15 and C 16 in said power capacitor group in turn, and thus a T-shaped structure is formed, said power capacitor group comprises four capacitors C 13, C 14, C 15 and C 36, and the respective other end thereof simultaneously connects with the respective emitters E of choppers IGBT 1, IGBT 2, IGBT 3 and IGBT 4 in said chopper group at one point, i.e., point D, said current limiter group comprises two current limiting inductors L 7 and L 8, and the output terminal of current limiting inductor L 7 is connectable to the zero line end N of the three-phase industrial AC power supply, while the output terminal of current limiting inductor L 8 is connected to one end of inductors L 4, L 5 and L 6 at one point, the anodes of the rectifiers Z1, Z2, Z3 and Z4 being connected to one end of inductors L 1,L 2 and L 3 at one point. said isolator group comprises eight isolators D 1, D 2, D 3, D 4, D 5, D 6, D 7, and D 8, wherein D 1 and D 5, D 2 and D 6, D 3 and D 7, D 4 and D 8 are respectively connected in series; the respective anodes of isolators D 1, D 2, D 3 and D 4 are respectively connected to the output terminals of respective corresponding resistors R 7, R 8, R 9 and R10 in turn, and the collectors C of choppers IGBT 1, IGBT 2, IGBT 3 and IGBT 4, in turn; the other sides of the resistors being connected to the cathodes of the rectifiers Z1, Z2, Z3 and Z4, in turn; and the cathodes of isolators D 5 and D 6 are connected to the input terminal of current limiting inductor L 7 in said current limiter group, while the cathodes of isolator D 7 and D 8 are connected to the input terminal of current limiting inductor L 8 in said current limiter group, the connection points of isolators D 1 and D 5, D 2 and D 6, D 3 and D 7, D 4 and D 8 connected in series in said isolator group are respectively connected to the respective one end of capacitors C 13, C 14, C 15 and C 16 in said power capacitor group in turn, and thus a T-shaped structure is formed, said power capacitor group comprises four capacitors C 13, C 14, C 15 and C 36, and the respective other end thereof simultaneously connects with the respective emitters E of choppers IGBT 1, IGBT 2, IGBT 3 and IGBT 4 in said chopper group at one point, i.e., point D, said current limiter group comprises two current limiting inductors L 7 and L 8, and the output terminal of current limiting inductor L 7 is connectable to the zero line end N of the three-phase industrial AC power supply, while the output terminal of current limiting inductor L 8 is connected to one end of inductors L 4, L 5 and L 6 at one point, the anodes of the rectifiers Z1, Z2, Z3 and Z4 being connected to one end of inductors L 1,L 2 and L 3 at one point.