The invention discloses an on-line detection method of 
continuous casting billet surface quality. According to the on-line detection method, a 
laser light source is taken as lightening equipment, an industrial-grade high-precision camera is used as 
image acquisition equipment, and a corresponding 
optical filter is arranged on the camera; when the surface of the 
continuous casting billet is exposed in 
laser beams, absorption, reflection and 
refraction features of 
oxide skin, cracks, recesses, scratches and 
slag pockets on the 
laser beams are different, and the difference is collected by the camera, and is shown in forms of imagines; and then defects observed in the imagines are positioned, sorted, preserved and underlined via defect detection 
algorithm. According to the on-line detection method, the 
laser light source with high power and the industrial 
linear array camera are combined, so that technological problems of 
continuous casting billet surface detection site imagine acquisition are solved; a 
distributed structure is used for 
data transmission, storage and 
processing, 
system stability is high, and storage and 
processing speed is fast; the imagine 
processing algorithm is firmly based on the features of detected objects, so that detection accuracy is high.