Branched-preformed particle gel（B-PPG）is a novel oil displacement agent，which has a crosslinked network and linear branched chains. When mixed with water or brine，B-PPG is not dissolved completely and the produced mixture is a heterogeneous suspension system. The rheological properties of B-PPG with different concentrations and different crosslinked degrees in brine were studied by steady shear and dynamic oscillation test；and the mechanism was also discussed from the viewpoint of molecular structure. The results show that B-PPG suspension has excellent viscoelasticity，salt tolerance and rheological properties. With the increase of crosslinked degree，the viscosity of B-PPG suspension decreases，as well as the frequency at crossing point of viscosity and elasticity（Fc）. High salinity makes the elasticity of HPAM solution decrease and has few effects on B-PPG，which proves that B-PPG has better salt tolerance. The viscosity and linear viscoelastic region of B-PPG suspension increase and Fc decreases with increasing concentration. Moreover，BPPG suspension shows weak gel character by linear fitting of dynamic oscillation curve.