Magnetic resonance imaging (MRI) is considered the best imaging method to evaluate the multifidus degeneration. The existing evaluation methods based on fat infiltration fraction (FSF) cannot fully reflect the muscle integrity and functional status. In order to obtain a tool for objective and continuous grading of multifidus degeneration. Fractal method was used to analyze the signal heterogeneity of multifidus. The fractal dimension of lumbar multifidus muscle（LMM） is closely related to LBP. The fractal dimension may be a reliable imaging marker for monitoring the degree of multifidus degeneration in symptomatic patients.