The objective of the present paper is to study the sweep effect on the blade design performance of a transonic compressor rotor. The baseline to be modified and swept is a designed well efficient transonic single rotor compressor. The first part of the present study is concerning the sweep effect with straight leading edge. In this case fixing the hub section the swept blade is formed by tilting the leading edge with whole blade forwards and backwards axially. The second part is to use an optimization strategy with simple gradient-based optimum-searching method and multi-section blade parameterization technique to search and generate an optimal swept rotor with curved arbitrary leading edge. Its adiabatic efficiency is a little bit greater than that of the reference un-swept rotor.