This　paper　was　based　on　the　text　results　of　12　different　section　size　columns　under　monotonic　loading　and　low　reversed　cyclic　loading.　In　order　to　study　the　effect　of　section　size　on　plastic　hinge　length,　four　methods　were　used　to　determine　the　plastic　hinge　length　of　the　specimens:　longitudinal　rebar　yield,　“longitudinal　rebar　strain-section　curvature”,　“dial　gage-section　curvature”,　equivalent　plastic　hinge　length.　The　analysis　results　show　that　the　four　methods　used　to　determine　the　plastic　hinge　length　have　certain　differences.　Result　of　equivalent　plastic　hinge　length　is　the　minimum;　result　of　method　“dial　gage-section　curvature”　is　the　maximum.　Plastic　hinge　length　relatively　decreases　with　increasing　of　cross　section　size.　Then,　on　the　basis　of　experiment,　the　section　size　effect　coefficient　of　plastic　hinge　length　was　proposed.