The compressibility of maize straw has great effect on the compressing processing, properties of products compressed, optimizing processing technology and designing compressing equipments of maize straw. The compressibility of maize straw rubbed was experimentally studied under certain initial density, different forms and different moisture contents with different compressing velocities. The relation curves of bulk modulus against compressing displacement and compressing density were analyzed by means of regressive analysis. Finally, the regressive mathematical model of compressibility was obtained. The results show that moisture content, initial densities and compressing velocities have obvious effects on compressibility of maize straw rubbed. Especially, when compressing density is larger than 230kg/m3, the compressibility of maize straw rubbed reduces significantly with increasing of compressing density.