Abstract: The present invention relates to a collision prevention method for a RFID system and a RFID system to minimize the collision of response signals by using sector antennas and controlling the power. The present invention comprises the steps of: separating plural tags in a space by setting up plural number of sector antennas; setting up the output stages of the power of each sector antenna to be increased in plural sequential stages; and reading a tag belonging to the output range by selecting a first sector antenna and transmitting minimum power among the set up stages. The present invention considerably reduce the collision probability of response signals of tags by dividing the tags in a space when a reader reads or writes tag information. The present invention also minimizes the time consumed to read/write tags and improves the communication distance and capacity.