Liquid-solid fluidized bed (LSFB) has been widely known and used to the separation of coarse coal particles (normally larger than 0.25 mm). The process of separation in LSFB needs fluidization water from the bottom to the top of LSFB. The fluidization water is formed by the water addition at the bottom of LSFB. Normally the quantity of water addition is very large, which increases the burden of water treatment in coal preparation processes. In this investigation, a spiral unit was introduced into the conventional LSFB and the new separation equipment was named S-LSFB. The spiral unit could provide an upward force for the upward movement of coarse low density coals into the concentrate, and hence the quantity of water addition for fluidization water may be reduced. Samples of 0.5-0.25 mm size fraction coal were used to investigate the difference in separation performance between S-LSFB and LSFB. It was found that the separation performance of S-LSFB was nearly equal to that of LSFB. S-LSFB may be beneficial to coarse coal separation in coal preparation plant since the burden of water treatment can be reduced by the application of S-LSFB.