Potassium-doped tungsten (KW), as an advanced candidate for first wall material, was developed to mitigate intrinsic embrittlement of bulk W. The addition of gaseous potassium bubbles (KBs) was known to act as effective barrier to the motion of irradiation damage and grain boundaries (GBs). The irradiation response to the He/H synergistic effect and the role of KBs on damage defects were two key issues when evaluating the performance of KW in future fusion reactors. In this work, KW was in-situ irradiated by 30 keV He+ and H2+ with He/H ratios of 2.5, 0.5, and 0.1 at 823 K. The synergy of He, H, and damage defects were discussed. The number density and the average size of irradiation-induced loops and bubbles nearby KBs, nearby GBs, and within the matrix was quantified. Increasing the ratio of H to He enhanced the nucleation sites of loops and promoted the accumulation rates of bubbles. The formation of a loop denuded zone nearby a KB was related to the KB size. The difference between the loop denuded zones nearby KBs and GBs was found. The estimated sink strengths of KBs and GBs were in line with our experimental results.