Several light incisions are brought up when the large size parts are scanned along the cross-section by laser light structure sensors.Since discrete points of each light incision are fitted to elliptic curve

the 3D coordinates of the central of the light incision plane can be attained.And with the space line fitting and error examination arithmetic

the large cross-section parts’straightness is gained.The geometry of cross-section can be recognized.The method of the measurement of the large-size parts’straightness by laser vision is brought forward

and on-line experiment result is also presented.