A silane composition for preparing a semiconductor thin films of a solar cell is disclosed. The silane composition contains a polysilane compound represented by the formula Si.sub.nR.sub.m (n is an integer of 3 or more, m is an integer of n to (2n+2) and an m number of R's are each independently a hydrogen atom, alkyl group, phenyl group or halogen atom, with the proviso that when all the m number of R's are hydrogen atoms and m=2n, n is an integer of 7 or more), and at least one silane compound selected from cyclopentasilane, cyclohexasilane and silylcyclopentasilane.