It is an object of the present invention to provide a high order silane composition that contains a polysilane having a higher molecular weight than conventionally, this being from the viewpoints of wettability when applying onto a substrate, boiling point and safety, and hence in particular enables a high-quality silicon film to be formed easily, and also a method of forming an excellent silicon film using the composition. The present invention attains this object by providing a high order silane composition containing a polysilane obtained through photopolymerization by irradiating a solution of a photopolymerizable silane or a photopolymerizable like-liquid silane with ultraviolet light. Moreover, the present invention provides a method of forming a silicon film comprising the step of applying such a high order silane composition onto a substrate.