Existing gas pocket detection approaches are based on visual observations of B-mode ultrasound images showing comparisons between normal soft tissue and gas pockets, which are time-consuming and dependent on operator experience. The present invention proposes an ultrasound system and a method of detecting a gas pocket. The ultrasound system comprises: an ultrasound probe (110) for transmitting an ultrasound signal toward the ROI and acquiring an ultrasound echo signal reflected from the ROI along a plurality of scanning lines; an obtaining unit (130) for obtaining a second harmonic component of the ultrasound echo signal for each depth of a plurality of depths along each scanning line of the plurality of scanning lines; and a deriving unit (140) for deriving a change in a center frequency of the second harmonic component along with the depth.