Improvement of dissolved concentration and mass transfer coefficient (K(L)a) of H-2 is a main strategy for efficient biogas upgrading process. In this study, Jet nozzle reactor (JNR) was applied to improve dissolved H-2 (DH2) concentration and KLa for successful in-situ biogas upgrading in an up-flow anaerobic sludge blanket (UASB) reactor. JNR could improve the DH2 concentration and KLa to 1.71 and 1.72 times higher than those of control reactor, respectively. Increased DH2 concentration and K(L)a contributed to increase CH4 content to 96.1% in UASB combined with JNR (JN-UASB). JN-UASB achieved maximum H-2 conversion efficiency of 97.9% and minimum H-2 content of 3.9% in biogas. Community of hydrogenotrophic methanogens and efficiency of H-2 conversion in JN-UASB were 1.1 and 1.3 times higher than those in control UASB (C-UASB), respectively. This study confirmed that DH2 concentration and K(L)a increased by JNR affected the improvement of H-2 methanation efficiency via rapid hydrogenotrophic methanogenesis. The findings of this study provide technical strategy and further research direction to upgrade biogas. (c) 2020 Elsevier Ltd. All rights reserved.