Abstract: A simulation code named DEST for hydrogen explosion was developed. The chemical reaction between hydrogen and oxygen was modeled by the one-step reaction model to improve calculation efficiency and ensure the calculation precision. The second-order additive semi-implicit Runge-Kutta method (ASIRK) was used to handle the stiffness of equations caused by source term. The stable and high-precision scheme, 5rd order WENO, was used to capture the parameter variations near the shock wave jump. The Newton-Raphson iteration technique was used to get the temperature of mixture, which reduced the number of iteration. The multi-blocking patching method was adopted to handle problems with complex geometry. Afterward, the one-step reaction model was tested and the recommended values for the model were given. Then DEST was applied to analysis of RUT facility. The results show that the reliability of DEST for transient analysis of hydrogen explosion is preliminarily proved.