The spores of 30 species of Arachniodes Bl.were observed under scanning electron microscope (SEM).The results showed that:(1)The spores of 30 species were bilaterally symmetric and monolete.The laesura is 1/2 to 3/4 of the equatorial diameter.The spore is elliptic or ovoid in polar view and semicircular or subrounded in equatorial view,(25.45～43.43) μm×(18.09～31.92) μm in size.(2)Seven types of surface ornamentations are identified,which are lamellate,echinate,rugulate,alate,lophate,auriculate,scabrate.(3)The relationships of some species which were disputed for a long time were discussed,a key based on the characters of spore morphology was also provided.The results implied that:A.leuconeura is reduced to the synonym of A.assamica;A.dayaoensis is reduced to the synonym of A.nipponica;A.falcata is as a part of A.nanchuanensis;The similar spore ornamentations shared by A.obtusiloba and A.sphaerosora suggested that they were related closely.