A detection apparatus comprises a freely-movable integral framework provided with front wheels and rear wheels, characterized in that, a control portion and a scan portion, and a driving mechanism driving said framework to move are provided on said framework, wherein said framework is provided with a first interface for connecting to external power, so that said detection apparatus is driven by external power via the driving mechanism to perform detection while conducting detection on site, and wherein the semitrailer for mounting the framework is provided with a second interface connectable to a traction apparatus so as to connect the detection apparatus and the traction apparatus while carrying out site-changing transportation. Said detection apparatus is not affected by the alteration of the emission standards, has low failure rate and maintenance cost, has zero emission in the detection state, and is pollution-free.