The invention provides a control device and technology for corner cracks of a microalloy steel sheet billet, and relates to the technical field of continuous casting and continuous rolling of steel sheet billets. The control device comprises a secondary cooling water distribution system, a corner efficient heat transfer narrow surface Gauss concave curved surface crystallizer and a crystallizer narrow surface foot roll zone new strengthened spraying system, wherein the new strengthened spraying system comprises a new water supply pipeline, a new strengthened spraying rack and a water distribution control system. In the control technology, dynamic water distribution is achieved through synergism of the corner efficient heat transfer narrow surface Gauss concave curved surface crystallizer,an integral strengthened cooling technology and a water distribution technology of the crystallizer narrow surface foot roll zone new strengthened spraying system and a wide surface integral slow cooling water distribution technology. According to the control device and the control technology, dispersion precipitation of microalloy carbonitride of corner structures of the cast billet can be stablyachieved, the corner structures of the cast billet are strengthened, narrow surface metals flow to side arcs during the large deformation pressing process of a liquid core of the cast billet, stressof the corner parts of the cast billet is reduced, and generation of the corner cracks of the microalloy steel sheet billet is radically controlled.