Polyacrylonitrile (PAN) is widely used in the preparation of ultrafiltration membranes. However, the hydrophilicity, thermal, and mechanical properties of the PAN ultrafiltration membrane are poor, limiting the applications in water treatment technology. In this study, the hydrophilic jute microcrystalline cellulose (MCC) is utilized as the modifier for the PAN membrane aiming to develop the ultrafiltration membrane with improved performance. The PAN/jute MCC ultrafiltration membranes with varying jute MCC contents are prepared using the phase inversion method and their structure and properties are systematically characterized. The results demonstrate that the hydrophilicity and thermal stability of the PAN membrane are enhanced. Under optimal conditions, compared with pure PAN membrane, the tensile strength and elongation at break of the membrane increase by 22.64% and 9.84%, respectively, and the water flux can reach 88 L/(m2 h), with the bovine serum albumin rejection ratio of 85%. The above results support that jute MCC can improve the performance of the PAN membrane significantly.