The tag collection algorithm in ISO/IEC 18000-7 has difficulty in collecting data from massive numbers of active RFID tags in a timely manner, so it should be improved to allow successful application in a wide variety of industrial fields. We propose two novel methods, a reduced-message method to improve the performance of data-tag collection and an efficient-sleep method to improve the performance of ID-tag collection. The reduced-message method decreases the slot size for a tag response by reducing the response size from the tag and reduces the number of commands issued from the reader. The efficient-sleep method utilizes redundant empty slots within the frame period to transmit sleep commands to the tags collected previously. We evaluated the performance improvement of tag collection by the proposed methods experimentally using an active RFID reader and 60 tags that we prepared for this study. The experimental results showed that the reduced-message method and the efficient-sleep method decreased the average tag collection time by 16.7% for data-tag collection and 9.3% for ID-tag collection compared with the standard tag collection. We also developed a simulation model for the active RFID system, reflecting the capture effect in wireless communication, and performed simulations to evaluate the proposed methods with a massive number of tags. The simulation results with up to 300 tags confirmed that the proposed methods could improve the tag collection performance, confirming the experimental results, even with larger numbers of tags.