Abstract: Using observed data of quiescent prominences with helical structure,the current properties of the quiescent prominences are studied with (i) the magnetic field inside prominences is force-free,(ii) the basic characteristics of prominence current is described by Kippenhahn-Schlu-ter model.The results are compared with Kuperus-Raadu model.They indicate that (1) the magnetic field and current inside prominences must be force-free;(2) Kippenhahn-Schluter model without mirror current may be a better model of quiescent prominebces;(3) there are two kinds of physical reasons causing the eruption of prominences.