In order to detect the large application of heating vertical needle pipe using in petrochemical,refinery industry,a kind of crawling mechanism which can solve the slender and needle pipes measurement is designed. A single driven wheel to stick on the way is used in the robot walking system,a pair of scissors hand structure is applied to adapt the change of pipe diameter between 50 ,90 mm. The dynamics analysis equation of the robot is listed,the best range of angle α between the center line and the horizontal line of the main driving wheel and the main wheel is obtained,the crawling system has the advantages of anti deviation,adjusting the different pipe diameter and the structure is simple.