Radio frequency identification (RFID) technology has many applications in inventory management, supply chain, product tracking, transportation, and logistics. One research issue of practical importance is to search for a particular group of tags in a large-scale RFID system. Time efficiency is a crucial factor that must be considered when designing a tag search protocol to ensure its execution will not interfere with other normal inventory operations. In this paper, we design a new technique called filtering vector, which can significantly reduce transmission overhead during search process, thereby shortening search time. Based on this technique, we propose an iterative tag search protocol. In each round, we filter out some tags and eventually terminate the search process when the search result meets the accuracy requirement. Furthermore, we extend our protocol to work under noisy channel. The simulation results demonstrate that our protocol performs much better than the best existing work.