A series of nanosized Co/Zn/Mn/K composite catalysts for Fischer-Tropsch synthesis (FTS) were prepared by supercritical fluid drying (SCFD) method and common drying (CD) method. The nanosized cobalt-based catalysts were characterized by XRD,TEM and BET techniques. Their catalytic performances were tested in a slurry-bed reactor under FTS reaction conditions. The drying and crystallization were carded out simultaneously during SCFD,therefore,the catalysts prepared by SCFD method have ideal structure and show the FTS performance superior to the others prepared by CD method. The FTS activity and selectivity were improved via adding Zn,Mn and K promoters,and less CH_4 and CO_2 as well as higher yield of C~(5+) products were achieved. The optimal performance of a 92% CO conversion and a 65% C~(5+) product yield was obtained over a catalyst with the component of Co/Zn/Mn/K = 100/50/10/7. Furthermore,the catalytic performance was studied under the conditions of liquid-phase and supercriticai phase slurry-bed,and C~(5+) product yield were 57.4% and 65.4%,respectively. In summary,better catalytic performance was obtained using the nanosized catalyst prepared by SCFD method under supercritical reaction conditions,resulting in higher conversion of CO,less CO_2 byproduct,and higher yield of C~(5+) products,