Abstract: Aim to optimize the secondary cooling scheme employed in continuous bloom caster for production of weathering steel for 310 Z-beam,which included the density of the secondary cooling and water distribution in secondary cooling zones,a series of improving measure was carried out.The improving measures include increasing the length of secondary cooling zones and the specific water flow,adjusting the water flow distribution among the secondary cooling zones,so the optimum secondary cooling control scheme is developed,which improves internal quality of bloom 310 Z-beam obviously.The practical operation shows that the ratio of center looseness ≤ 1.0 is increased from 79.71% to 90.70%,the ratio of central segregation<0.5 is increased from 1.45% to 44.19%,the free central shrinkage cavity is increased from 86.96% to 93.02%,while,the free center line crack is increased from 39.13% to 62.79%,the free intermediate crack is increased from 85.51% to 88.37%, the free sub-surface crack is increased from 78.26% to 97.67%,and the free comer crack is increased from 73.91% to 93.02%.The qualified blooms are delivered to produce 310 Z-beam which R_eL is ≥ 450 MPa.