AbstractThree methods to establish the vertical datum of the crustal motion are put forward and investigated. The systematic errors are calculated between some vertical velocity fields and the reference datum of vertical motion of the crust, and the reasons for the diversity of systematic errors are analyzed. The reference datum of vertical motion of the crust that are established based on three different principles are analyzed and compared, viz. taking SLR vertical velocity fields as reference datum of vertical motion of the crust; taking vertical velocity predicted by postglacial rebound ICE-4G geophysical model as reference datum; taking the vertical velocity constrained as zero which located nearby the low latitude belts of equator (−10°∼ 10°) as reference datum. The result shows that there is a better consistency of those three methods in whole, and the reference datum of vertical motion of the crust based on SLR vertical velocity has advantages like clear geophysical sense, easy implementation and application.