Multi-interlayer and large amount of unsolvable materials are the China's salt rock's specialties, so that the current software is not able to simulate the process that how domestic layered salt rock cavity built clearly. By using the theory of hydrodynamics and chemical kinetics, a mathematical model which has excellent ability to describe the cavity building process of salt rock, and a criterion of interlayer collapse are proposed. Then by combining the specificity of the domestic washing techniques, an improved simulation software: Salt Cavern Builder V1.0 is developed. This software has the ability to simulate the cavity building process of pure salt rock and multi-layered salt rock. This software has outstanding capability to present the result in every step for designing cavity-building scheme. By testing the process of similar cavity-building experiments for large-size molded salt rock, the cavity-expansion processes for both none-layered and simple-layered salt rock are simulated successfully. Based on similar theory, this cavity-building simulation software can obtain satisfactory result under the condition of the cavity-building technique in the field. The result is very closed to the one produced by real experiment, so as to verify the practicality of this software.