We　theoretically　study　the　influence　of　the　spin　-　orbit　coupling　(SOC)　on　the　in-plane　optical　anisotropy　(IPOA)　induced　by　in-plane　uniaxial　strain　and　interface　asymmetry　in　(001)　GaAs/AlGaAs　quantum　wells　(QWs)　with　different　well　width.　It　is　found　that　the　SOC　has　more　significant　impact　on　the　IPOA　for　the　transition　of　the　first　valence　subband　of　heavy　hole　to　the　first　conduction　band　(1H1E)　than　that　of　1L1E.　The　reason　has　been　discussed.　The　IPOA　of　(001)　InGaAs/InP　QWs　has　been　measured　by　reflectance　difference　spectroscopy,　whose　amplitude　is　about　one　order　larger　than　that　of　GaAs/AlGaAs　QWs.　The　anisotropic　interface　potential　parameters　of　InGaAs/InP　QWs　are　also　determined.　The　influence　of　the　SOC　effect　on　the　IPOA　of　InGaAs/InP　QWs　when　the　QWs　are　under　tensile,　compressive　or　zero　biaxial　strain　are　also　investigated　in　theory.　Our　results　demonstrate　that　the　SOC　has　significant　effect　on　the　IPOA　especially　for　semiconductor　QWs　with　small　well　width,　and　therefore　cannot　be　ignored.　©　2014　Chinese　Physical　Society　and　IOP　Publishing　Ltd.