Disclosed is radio frequency identification (RFID) middleware system and method of detecting the load of reader connections occurs during the middleware is running and balancing the load in real-time so as to minimize a decrease of the performance of the RFID middleware system. The RFID middleware system comprises: a client; a RFID middleware; RFID readers; and RFID tags, wherein the RFID middleware comprises: a middleware engine which filters tag events collected according to queries registered in the client; and a reader framework which detects the load of the connections of the RFID readers occurs while the RFID middleware is running and balances the load in real-time.