By　conducting　the　experiments　of　circular　transmission　line　method　(CTLM)　on　samples　with　different　thicknesses　of　p-InGaN,　we　find　that　the　specific　contact　resistance　between　p-InGaN　and　Ni/Au　increases　as　the　thickness　of　InGaN　increases.　When　the　thickness　of　InGaN　is　less　than　a　certain　value,　the　specific　contact　resistance　between　p-InGaN　and　Ni/Au　is　lower　than　that　of　p-GaN＇s.　It　is　attributed　to　the　situation　that　the　tunneling　barrier　width　is　drastically　reduced　by　polarization-induced　electric　fields　in　the　strained　p-InGaN　layers　resulting　in　an　increase　of　the　hole　tunneling　probability　through　the　barrier　and　a　significant　decrease　of　the　specific　contact　resistance.　However,　by　the　infection　of　the　surface　morphology　of　the　samples　and　the　intrinsic　surface　electron　accumulation　of　InN,　the　contact　characteristics　become　worse　when　the　thickness　of　InGaN　excesses　the　critical　thickness.