Structured uncertainty with repeated complex scalars is proposed to describe the linear time-invariant systems with incommensurate delays. By means of the D -scaled upper bound， linear fractional transformation and frequency-sweeping test， stability regions in delay space are found. Based on theorem， necessary and sufficient conditions for the single delay system and less conservative sufficient conditions for systems with multiple incommensurate delays are provided. Simulation results of the tests and the power system stabilizer（PSS） system with incommensurate communication delays are reported to validate the methodology.