Abstract: The worldwide up-to-date online detection technology of wax deposition in the subsea pipeline is investigated by the authors. The location of wax deposition can be accurately predicted by the pressure wave transmission technology, while the prediction of the wax plug length and scale is of low reliability. Radioactive isotope can be used to predict the location and the thickness of the wax deposition online, and the detection is more reliable. Heat impulse technology can realize a continuous measurement of the wax deposition with a high reliability. Present online detection technologies are mainly usedin the model loop tests, and are seldom applied in the real subsea pipelines. Because the subsea pipeline is far away from the platform, the remote detection technology has a promising future.