We studied the fully coupled tripartite hybrid system with a two-level atom embodied in cavityopto-mechanical system. Applying the Shriever-Wolff approximation to the Hamiltonian of the sys-tem, we reached a fully diagonal effective Hamiltonian as well as its eigensystems. Thus the systemhas two turnable parameters including the detunings between the atom, cavity resonant frequencyand the driving laser field. We investigated the single- and two-photon blockade effects of the sys-tem under different detunings and cavity field driving strength using the probabilistic amplitudemethod and the quantum master equation method. The two-level atom plays an important role forthe photon blockade effect because it induces a shift of the cavity resonant frequency and a moreadjustable parameter for the system.