The emission spectrum of a single atom in the nonlinear coupling J-C (Jaynes-Cummings) model including any forms of nonlinearities of both the field and the intensity-dependent atom-field coupling is studied.The effects of nonlinearities on the spectrum are demonstrated.It is shown that features of the emission spectrum are influenced significantly by the kinds of the field nonlinearity term R(a+a) and the intensity-dependent atom-field nonlinear coupling factor f(a+a).The structure of the spectrum is quite different from that of the standard J-C model.It is found that when f(a+a)=1/(a+a)1/2,the emission spectra always show the definite three-peak structure for any initial state of the field,which implies that the effects on the emission spectrum of both the specific intensity-dependent nonlinear medium with f(a+a)=1/(a+a)1/2 and the initial field photon statistics can be counterbalanced.This feature is analyzed with an analytic method.