Abstract: The accident source term evaluation code can only evaluate single accident and output the evaluation result for given release routes, and requires complex pretreatment and special input card. To resolve these problems, BP-ASTE code which can simulate isotope radioactivity in each containment and isotope radioactivity release rate from containment to joined containment following accident evolution is developed based on accident sequence and matter and energy release. The example of SGTR accident is given to illuminate the establishing and implement of BP-ASTE code.