A novel combination consisting of microbial polysaccharide (diutan gum or xanthan gum) and branchedpreformed particle gel (B-PPG) was systematically investigated by rheological method. Polysaccharide/B-PPG suspensions exhibit pseudoplastic fluid characteristics. Synergy occurs between polysaccharides and B-PPG on thickening the suspensions. The salt tolerance is improved by combining xanthan gum and B-PPG, and both of the temperature tolerance and salt tolerance are enhanced by combining diutan gum and B-PPG. The combination of diutan gum and B-PPG contributes to the formation of strong particle gel networks based on double helices and gel particles by van der Waals force and hydrogen bonding, improving the stability in high-temperature and high-salinity environments. It was confirmed that the heavy oil recovery efficiencies of diutan/B-PPG composite (17.4% original oil in place (OOIP)) and xanthan/B-PPG composite (8.2% OOIP) were higher than that of B-PPG alone (5.3% OOIP) at 90 degrees C and 244,121 mg.L-1 salinity. (C) 2019 Elsevier Ltd. All rights reserved.