Wax　deposition　is　a　severe　flow　assurance　challenge　that　threatens　waxy　crude　oil　production　and　transportation.　For　wax　remediation,　pipeline　pigging　is　the　most　widely　used　technique.　However,　the　elusiveness　of　wax　removal　mechanism　and　the　lack　of　reliable　methods　to　evaluate　wax　breaking　force　and　wax　removal　efficiency　easily　trigger　pig　stalling　and　wax　blockage　in　field　pigging　operations.　Modeling　wax　breaking　force　and　wax　removal　efficiency,　therefore,　promotes　the　pigging　confidence.　This　Review　seeks　to　clarify　the　current　picture　of　wax　removal　research　in　crude　oil　pipeline　pigging.　Relevant　wax　deposit　properties　including　wax　layer　thickness　and　strength　are　discussed.　Wax　removal　mechanisms　are　summarized　from　perspectives　of　wax-pig　interaction,　macroscopic　force　response,　and　scenarios　with　oil　flow.　Prediction　models　of　wax　breaking　force　and　wax　removal　efficiency　are　analyzed　comprehensively.　Pig　geometry　optimization　using　this　model　is　given.　In　addition,　the　key　roles　of　wax　deposit　strength,　viscoelasticity　and　thixotropy,　foam　pig　investigation,　and　wax　plug　prediction　are　highlighted　for　guiding　future　endeavors　in　this　area.