This paper investigates the robust control synthesis problem of nonhomogeneous Markovian jump systems with actuator saturation and uncertainties. First of all, to make a comprehensive mode-transition description, three separate mode sets are established according to the property of transition rates. And then, to improve the numerical solvability of inequality conditions dependent on time-varying transition rates, two useful relaxation methods are developed on the basis of the mode sets. Especially, by taking advantage of a new zero-sum constraint, the relaxation process is further evolved such that the conservatism arising from incomplete knowledge of transition rates can be reduced. Lastly, this paper provides the LMI-based conditions capable of estimating the attraction domain as well as of designing a mode-dependent robust control.