The invention belongs to the technical field of super-large-scale integrated circuit manufacturing, and in particular relates to an ultra-low dielectric constant material film and a preparation method thereof. The preparation method comprises the following steps of: first, taking a single annular 2,4,6,8-tetravinyl-2, 4, 6, 8-tetravinylcyclotetrasiloxane as a precursor; then, forming a precursor film on a silicon substrate by a spin-coating method; next, irradiating the obtained film by using ultraviolet light; later on, performing polyreaction among precursor monomers to form an ultra-low dielectric constant SiOCH film; and finally, performing thermal annealing treatment on the film to further improve the electrical characteristics of the SiOCH film. In the SiOCH film obtained by adopting the method, the dielectric constant can reach 1.94 and the breakdown electric field intensity is greater than 3 MV / cm; and under the external electric field of 1 MV / cm, the film has the leakage current density magnitude order of 10<-7>A / cm2, the young's modulus of greater than 2 GPa, and the hardness of 0.2 GPa.