Rigorous mathematical analysis and numerical simulations were used to study the codimension2 foldHopf bifurcation in the chaotic Rossler system. Through simple calculation, the coordinates of three equilibria were obtained firstly. Then the origin of coordinates was translated to the equilibrium studied later using the change of variables. Parameter conditions for the foldHopf bifurcation were specified by analyzing the Jacobian matrix of the new system after transformation. Moreover, some extra nondegeneracy and transversality conditions were verified for the chaotic Rossler system possessing the codimension2 foldHopf bifurcation under specified parameter conditions. With the help of a complex variable, the Rossler system can be brought into the normal form and the corresponding bifurcation diagram can also be obtained. For the bifurcation parameter conditions derived theoretically, numerical simulations show that the foldHopf bifurcation indeed occurs in the Rossler system, which confirms the results of the theoretical analysis.