In order to reveal the pores complex structure of biochar-amended soils and its influencing factors, the saline/sodic soil in the coastal reclamation area of Jiangsu Province was taken as the research subject. In this study, the surface soils (0-20 cm) were amended by thoroughly mixed biochar with three application rates (0, 2% and 5% by mass of soil, respectively) in a completely randomized design. After harvesting rice in October each year, the surface layer (0-20 cm) of undisturbed soils was taken using a plastic ring and the CT pore series of the soil was obtained through Micro-CT scanning. Based on multifractal detrended fluctuation analysis and data rearrangement, the influence of biochar addition on the multifractal characteristics and their source of CT-porosity series was analyzed. The results showed that the complexity of pore series for each treatment increased with year. Compared with 0 and 5% biochar treatments, the complexity of CT pore series in 2% biochar treatments increased by 7.54% and 5.28%, respectively. Both probability density function and long-range correlation influenced the multifractal characteristics of CT pore series. Long-range correlation between pore and space was the main influencing factor. The addition of biochar made the pore fractal characteristics more susceptible to the influence of microbial activities in soil. This study could provide a theoretical basis for analyzing the pore structure of saline soil with biochar.