The invention concerns a method and a device for acetylene cutting of continuous cast billets, which consists in positioning relative to the billets to be cut (1) a cutting element (8) and a trimming element (9) using a direct reference hold on the billet (1) by means of a mobile clamp (7), then lowering the cutting element (8) and the trimming element (9) parallel to the lateral surfaces of the billet so as to gradually produce a cut from above downwards by a horizontal engagement of the lateral surface of the billet, and simultaneous trimming of the cutting line being formed on the other lateral surface by an engagement of said other lateral surface constantly directed downwards.