Float Valve Sub is an important tool in petroleum exploration and drilling engineering. The float valve sub is connected at upper part of drill bit. The float valve sub is near the bit connecting thread. The float valve sub can also be used at different necessary position of drill string when required. The main application is, when connected with single piece pipe, it prevents mud from coming in and up blocking the hole. When blowout takes place, blowout in drill string will be avoided because nozzle is closed automatically by valve cap of the float valve assembly .