At the tip of the turbine blade, there are leakage flow and secondary flow, the interaction between which has significant influences on the flow and heat transfer of tip region. While casing boundary layer is the main source of secondary flow,  the length of import segment, the wall conditions of casing and tip clearance height are changed to adjust the strength of leakage flow and secondary flow in order to analyze the effects of casing boundary layer on blade tip region flows, particularly tip wall heat transfer. Calculations have been performed on the GE-E3 first stage high pressure turbine rotor and the result shows that the interaction between leakage flow and secondary flow has noticeable effects on the tip heat transfer of the suction surface side, and both reducing secondary flow and increasing leakage flow can decrease the tip heat transfer on the suction surface side but enhance the tip heat transfer on the pressure surface side. In addition, the influence of the radiused edge blade on the tip leakage flow and heat transfer has been discussed in order to provide a reference for the analysis of the tip flow and heat transfer in the multilevel and complex casing conditions.