The present disclosure provides a method and a device for controlling a power factor on motor side and a system having the same, and the method includes: controlling the motor using a control approach of Id′=0 so as to obtain quadrature-axis voltage Uq′ and direct-axis voltage Ud′ in a virtual coordinate system of a current control cycle; calculating a first control value according to Uq′ and Ud′; obtaining a power factor control target value, and calculating a target control value according to the power factor control target value; performing a PI control on a difference between the target control value and the first control value so as to obtain a coordinate deviation angle, and overlapping the coordinate deviation angle to a motor angle of the current control cycle so as to build a virtual coordinate system of a next control cycle, such that the power factor on the motor side is controllable.