An electric motor driving system with no electrolytic capacitor, and a field weakening control method and control apparatus thereof. The method comprises: acquiring a current direct-current bus voltage in an electric motor driving system in real time (11); according to a known correlation between a direct-current bus voltage and an integral coefficient of a processor, acquiring an integral coefficient corresponding to the current direct-current bus voltage and acting as a current integral coefficient (12); obtaining a target field weakening current according to the current direct-current bus voltage, a current target voltage and the current integral coefficient (13); and executing field weakening control over the electric motor driving system according to the target field weakening current (14). By means of the control method and apparatus, requirements for the control of the electric motor rotation speed of an electric motor driving system with no electrolytic capacitor can be met.