It is the main purpose of this paper to calculate the energy splitting of ground state and excited states induced by thermally assisted quantum tunneling . first , a brief introduction is given for the theoretical and experimental studies on the magnetic macroscopic quantum effects . then , spin tunneling in a uniaxial ferromagnetic particle in transverse magnetic field is converted to a pseudoparticle moving in effective double - well potential with the help of the effective potential description of quantum spin systems developed by ulyanov and zaslavskii . finally using the periodic instanton method we evaluate the transition amplitude , energy shift and prefactor of wkb exponential and the energy splitting of ground state and the tunneling rate for excited states induced by thermally assisted quantum tunneling are obtained 文章首先对磁性宏观量子效应的理论和实验方面作了简单介绍，然后借助于ulyanov和zaslavskii发展的一种等效势描述方法，把外磁场沿难磁化轴方向时的自旋隧穿约化成在等效双势阱中运动的粒子，利用瞬子方法给出基态能级劈裂，最后利用周期瞬子方法分别计算了隧穿幅、能级移动以及wkb前因子，从而给出由于热助量子隧穿引起的激发态的隧穿率。
