The adsorption characteristics between extracellular polymeric substances (EPS) and microplastics polystyrene (PS) in anaerobic granular sludge were studied. In anaerobic granular sludge, the smaller the particle size of microplastics, the more obvious the increase of total EPS. 0.5 um PS promotes an increase in EPS to 1.14 times that of the blank reactor, 200 um PS reduces the EPS to 0.91 times. Among the five fractions of EPS, the hydrophilic fraction (HPI) fraction can resist the toxicity of small size microplastics, so the increment is the most obvious. 5 um PS promotes an increase in the relative intensity of HPI from 55.5 mg/gVS to 87.2 mg/gVS. The adsorption behavior of the five fractions of EPS on microplastics PS can be well described by pseudo-second-order kinetics model and Freundlich model. Hydrophobic interaction, π-π electron-donor-receptor interaction, chemical adsorption and electrostatic attraction simultaneously affect the adsorption of five fractions of EPS by PS. The analysis of infrared spectroscopy, which showed that O-H stretching vibration, carbonyl C-O group, amide-1, amide-2 absorptivity, and phenol C-O bond have a great contribution to the adsorption of microplastics. It can be seen that small particle sizes of PS have a more significant impact on sludge EPS.