Abstract: During continuous casting of micro-alloyed steel thin slabs, the corner cracks occur frequently, which would cause the quality defects such as scar and cracks at the edges of the hot-rolled coils, and has been a common technical issue in steel industry. In the present work, the characteristics of the micro-structure and carbonitride precipitation of the thin slab corner of Qste380TM low carbon niobium-titanium micro-alloyed steel, as well as the reduction of area of the steel under different cooling and tensile rates were detected. Moreover, the evolutions of temperature and stress of the solidified shell in different structure molds and secondary cooling processes were simulated. The results show that there is a significant third brittle temperature zone during continuous casting of micro-alloyed steel thin slabs, and the greater the deformation rate, the more significant the third brittle temperature zone is. Under the conventional thin slab continuous casting process, the cooling rate of thin slab corners in upper part of mold and in the secondary cooling zone from mold exit to liquid core reduction segment is so lower to lead a chain of niobium-titanium carbonitrides precipitate at the grain boundaries of the corners. During the process of liquid core reduction, the low plasticity corners crack because of large deformation and stress. Applying the Gaussian concave curved surface mold, which the narrow face copper plates could efficiently compensate the shell shrinkage, and the foot roll zone hard cooling process increase the relatively cooling rates of the slab corners over 10 ℃/s and 20 ℃/s, respectively. As a result, the carbonitrides precipitate in slab corners dispersedly, and the reduction stress of slab corners reduces since the new mold promotes the metal flow of slab narrow surface broadsiding during the liquid core reduction, finally the cracking rate of the corners during the micro-alloy steel thin slabs casting has been reduced significantly.