An ultrasound system and method for generating an elastic image are disclosed. The ultrasound system includes an ultrasound probe and a processor. The ultrasound probe is configured to transmit ultrasound signals into a target object and receive ultrasound echo signals from the target object while the ultrasound probe applies a variable compression force on the target object. The processor is configured to set a Doppler gate at a predetermined location in an image of the target object, generate a plurality of frames of B-mode ultrasound data while the variable compression force is applied on the target object based on the ultrasound echo signals, generate a plurality of frames of Doppler-mode ultrasound data based on the Doppler gate while the variable compression force is applied on the target object based on the ultrasound echo signals, determine a period for a cycle of the variable compression force based on the Doppler-mode ultrasound data, select two frames of the B-mode ultrasound data based on the period, and generate an elastic image of the target object based on the selected frames of the B-mode ultrasound data.
