Hot applied, and modified asphalt sealant is produced by adding polymer modifier, synthetic rubber or recycled rubber, extender, and plasticizer to asphalt, and by promoting hot-endurance and cold-endurance so that it can adhere to the asphalt and concrete road. The factors which affect quality of sealant in the course of sealant production are as followings.(1) Quality of asphalt (2) Characteristic of synthetic rubber (3) Oxidization of sealant (4) Quality controlIn conclusion, it can be said that know-how of sealant producing company is how factors mentioned above are controlled so that it can produce sealant excellent in quality and efficiency.