采用相干态正交化展开方法，研究了非旋波近似下V型三能级原子与单模腔场的相互作用,并且利用保真度对能级的交叉问题进行了判断.研究了在二项式光场作用下，V型三能级原子初始状态以及二项式态光场的光场系数对光场二阶相干度的影响.数值计算结果表明：原子初始时刻处于基态时，随着η的增大光场呈现聚束效应的持续时间先增大后减小；原子初始时刻处于叠加态时，随着参量η的增大光场呈现聚束效应的持续时间逐渐减弱；当η的值足够大时，在这两种情况下光场都将完全呈现反聚束效应;当其它参量不变时，G2(t)的平均值会随着耦合强度的增大而增大.

By the method of coherent-state orthogonalization expansion, the energy spectrum of the V type three-level atom was calculated exactly in the non-rotating wave approximation, and a level-crossing problem was also considered by means of fidelity. The influences of the initial states of the V type three-level atom and the parameter of the binomial optical fields on the second-order coherence degree were studied. The numerical results indicate that: when the atom is initially in the ground state, the duration of the bunching effect increases at the beginning and then decreases with the increasing of η; when the atom is initially in the coherent state, the duration of the bunching effect decreases with the increasing of η. Finally, both cases of the light fields displayed anti-bunching effect completely when the value of η was large enough. When other parameters didnot change,the average of G2(t) increases with the enlargement of coupling strengh.