Considering the atomic coherences and injected classical field, we derived the n-Onphase-locking Lorenz-Haken equation by using the technique of stochastic differential equations. The effects of detuning, injected field and the atomic coherence on the dynamical characteristics of this equation is then numerically studied. The results show that in laser working situations, the detuning can result in chaotic behaviors of the light phase. Under different conditions, the system can generate four attractors, double attractors and single attractor, and the fractal dimension of the system is larger than that of the locking-phase system. The optical detuning, injected field and atomic coherence can inhibit the chaos of the cavity field. In the optical bistability regions, we obtain symmetric bistability pair, but never find the chaotic attractors.