The effect and the mechanism of the central temperature of the surface irradiated area by laser on boundary crack and microstructure of WC/Co ceramic cladding layer on the surface of M2 high-speed steel cutter are studied. The ceramic cladding layer are fabricated on the surface of M2 high-speed steel cutter by IPG fiber laser system, the multi-factor laser process parameters are coupled, the cladding layer are analyzed by the central temperature of the irradiated area on the cutter substrate surface(T) and central temperature of unit mass powder(η), and the macroscopic morphology, microhardness and microstructure of the cladding layer are characterized by microhardness meter and SEM, EDS. When the T is less than 3535 K, the cladding layer usually exhibits unilateral crack; when the T reaches 4329K, the crack length and width of the cladding layer increase exponentially and expand along the bonding line. When the T reaches more than 5009 K, the number of longitudinal penetration cracks in the cladding layer increases, and large area tissue defects begin to appear inside the cladding layer. When the η is 19 884 K/g, the maximum microhardness of the cladding layer is 1400HV; when the η is less than 19 884 K/g, the maximum microhardness of cladding layer and the central temperature of unit mass powder were almost equal growth trend to each other, and the microstructure of the cladding layer is mainly irregular WC cellular crystal and W2C dendrite as the main strengthening phase. When the η reaches more than 19 884 K/g, the maximum microhardness value of the cladding layer decreases gradually, and the tissue in the cladding layer continues to grow and begin to agglomerate, and gradually forms a massive structure with WC as the main strengthening phase. When the η exceeds 23 614 K/g, the WC rich ceramic layer appeared in the left and right boundary bound region of the cladding layer. When the central temperature of the irradiated area is less than 3535 K, the cracks in the WC/Co ceramic layer can be controlled stably at the boundary of the cladding layer. The source of the bonding crack is mostly the left and right boundary of the cladding layer and the substrate, and the crack extends along the cladding bonding line with the increase of central temperature. The effect of central temperature of unit mass powder on the highest microhardness of ceramic cladding layer is most obvious. When the central temperature of unit mass powder is low, the ratio of the laser temperature gradient to the melting rate has a higher effect on the microstructure and microhardness of the ceramic cladding layer; when the central temperature of unit mass powder is high, the melting rate has a higher effect on the microstructure and microhardness of the ceramic cladding layer. The formation and propagation of boundary cracks in ceramic cladding layer are related to the physical parameters difference of physical parameters of cladding layer and substrate, the change of temperature gradient, the warping deformation of substrate, and the distribution of ceramic phase.