Synchronous explosion forming, which takes advantage of the thixotropy of concrete or cement mortar and the condensability of soil under blasting concussion, is a newly developed method to construct underground cavities. In this paper, the mechanism of the new method is elucidated first, and then the zonal characteristics in soil are investigated emphatically. In order to accomplish comparative analysis, both synchronous explosion forming and conventional compression blasting experiments are conducted under same soil and explosive conditions. Experimental results indicate that the zonal characteristics in soil by synchronous explosion forming differ from that of by conventional compression blasting. When the new method is applied, formation and growth of cracks in soil during blasting is restrained, and the crannied region, which is usually produced in conventional compression blasting can be substituted by a soil- cement mortar occlusive region. Additional, the compaction range in soil is large when the new method is used. The zonal characteristics of synchronous explosion forming are more advantageous to the bearing capacity of soil and secular stability of cavity.