Abstract: Correcting Emanuel's Wave-CISK scheme by consideration of condensation heating only for the updrafts of band-shaped convective systems and treatment of instability in the framework of initialization, a quasi-two-dimensional nonhydrostatic model was used to disscuss the effect of the amplitude of heating and its vertical distribution on the development,evolution, migration and structure of symmetric instibility (SI). Assuming a basic state of symmetric stability, the model is zo-layered in the vertical with horizontal grid intervals of 5 km, defined by rigid top and bottom boundaries and periodic one in the horizontal. For the two experiments with difference only in the amplitude of heating,the greater the amplitude, the stronger the diabatic heating becomes,resulting in different layers of preference with respect to the CISK feedback. By fixing all conditions other than the vertical distribution of heating, a third experiment shows a slower growth rate in disturbances.