This paper offeres an exact study on the robust stability of a kind of combined integrating control system, and the robust stability belongs to the analysis of a kind of quasi-polynomial with two independent time delays. The parameters of stable space under time delay uncertainty are luted after Rekasius transformation, and then a new cluster treatrnent of characteristic roots ( CTCR ) procedure is adopted to determine the stable space. By this strategy we furl that the unstable space is not continuous and both Katitonov vertices theory and Edge theory are unable to he extended to quasi-polynomial under time delay uncertainty.