Incoherent multimode bistable soliton can exist in higher-order nonlinearity media. Using the coherent density method, we obtain the analytical expression of the incoherent multimode bistable soliton, and the higher-order nonlinearity controls the existence and the intensity peak of bistable solitons. We find the cut-off wavelength, the minimum width of the incoherent beam and the nonlinearity condition for the media, and then we study the propagation characteristics of coherent components that consist of incoherent multimode beams. According to the stability criterion, we demonstrate rigorously that the incoherent multimode bistable soliton can propagate stably against small perturbation.