Hydrogen　is　regarded　as　one　of　the　most　potential　alternatives　for　high-efficiency　and　eco-friendly　combustion.　The　influences　of　hydrogen　fractions　and　equivalence　ratios　on　chamber　pressure,　combustion　phases,　wall　heat　loss,　brake　thermal　efficiency,　and　cyclic　fluctuation　of　Wankel　engines　were　studied　by　testbench　measurement.　The　intrinsic　mechanisms　of　these　effects　were　analyzed　through　numerical　investigation.　Results　indicated　that　increasing　hydrogen　fraction　increased　the　mass　fraction　of　high-temperature　regions,　the　timings　taken　for　formations　of　intermediate　products　were　advanced,　and　the　peak　H2O2　and　CH2O　reduced　while　OH　concen-tration　increased.　These　factors　were　responsible　for　increased　chamber　pressure　and　the　shortened　flame　development　and　propagation　periods　in　experiments.　A　close　inverse　relationship　can　be　drawn　between　the　wall　heat　loss　and　brake　thermal　efficiency　with　respect　to　hydrogen　addition.　A　larger　hydrogen　fraction　coupled　with　a　smaller　equivalence　ratio　manifested　lower　wall　heat　loss　and　higher　thermal　efficiency.　Compared　with　hydrogen-free　regimes,　brake　thermal　efficiency　of　6%　hydrogen　fraction　was　increased　by　64.6%.　There　was　a　positive　proportional　correspondence　between　the　initial　flame　development　and　cycle-to-cycle　fluctuation.　Increasing　the　hydrogen　content　caused　the　enhanced　turbulent　intensity　during　the　initial　combustion　stage,　which　contributed　to　the　stability　improvement　of　engine　operations.