This paper explores the mechanism of force chain evolution and voidage change under vibrational and non-vibrational compression conditions of rice straw of different lengths. Simulations were used to explore the force chain evolution and voidage variation mechanism under different conditions. The results show that under non-vibrational compression, the strong force chain passes from top to bottom in vertical direction and from center to periphery in tangential direction. Under vibrational compression, the force chain passes from top and bottom to center in vertical direction and the force chain evolves from outer ring to interior and exterior in tangential direction. The number of strong chains, voidage and standard deviation of the mean pressure under vibratory compression are lower than the values under non-vibratory compression. Vibration promotes stress transfer and enhancement, velocity enhancement and density enhancement. This study analyzes the mechanical properties of different lengths straw during vibrational and non-vibrational compression from a detailed viewpoint.