Abstract: A new mold powder was developed in continuous casting production. Being skeleton particles in the mold powder, carbon particles were replaced by B particles. The new mold powder was similar to the conventional mold powder in thermal insulation, melting characteristics, viscous characteristics, inclusion absorption ability and crystallization property. New mold powder can solve the problem of surface carbonization and carbon pick-up of the mold for ULC steel. The new powder has no problems of surface boronization of the mold and boron pick-up for ULC steel. B particles can increase JRBW and A2O3 absorption rate, and can decrease melting rate, viscosity, melting temperature, and solidification temperature, crystallization temperature of the mold powder.