A collision avoidance system and collision avoidance method for a detection bed are described. The collision avoidance system comprises stress sensors for measuring a stress caused by supporting a bed face of the detection bed and outputting stress data; a collector, which is connected with the stress sensors and is configured to collect the stress data output by each of the stress sensors; a judging processor, which is connected with the collector and is configured to judge whether the collected stress data monotonically changes within a preset time; and a controller connected with the judging processor, the controller controlling the bed face of the detection bed so that it stops moving when the judging processor determines that the collected stress data monotonically changes within the preset time.