This　paper　is　based　on　the　experiment　results　observed　from　15　different　section　size　beams　subjected　to　the　monotonic　loading　and　the　low　reversed　cyclic　loading.　In　order　to　study　the　effect　both　on　the　section　size　and　the　variation　laws　for　the　plastic　hinge　length,　four　approaches　were　used　to　explore　the　variation　laws　when　the　load　surpassed　the　yield　point　of　the　reinforcement　to　the　limit　displacement　point.　The　analysis　results　show　that　after　the　yield　load,　the　more　the　increase　of　the　load,　the　more　the　increase　of　the　plastic　hinge　length.　It　means　that　the　plastic　hinge　length　shows　the　size　effect　obviously.　When　section　heights　increase　from　200　mm　to　1　000　mm,　the　relative　plastic　hinge　length　of　the　specimens　subjected　to　the　monotonic　loading　shows　that　the　peak　load　point　and　the　limit　displacement　point　are　reduced　by　40%　and　by　44%,　respectively,　and　by　38%　and　by　40%　for　the　low　reversed　cyclic　loading.　The　results　calculated　from　the　proposed　approaches　which　are　considered　to　be　the　influential　factor　of　the　sectional　height,　agree　well　with　the　experimental　results.　©,　2015,　Beijing　University　of　Technology.　All　right　reserved.