A new concept of undercooling heredity is developed to evaluate the undercooling ability in a non catalytic nucleation coated mould, where alloy melts were highly undercooled previously. Before the heredity experiment a non catalytic nucleation composite glass lined coating (B F) was prepared on the inner surface of mould and the Cu 70 Ni 30 alloy was selected to perform undercooling experiment in the B F non catalytic coating mould. Its ratio of undercooling heredity was 0.76. The results prove that the B F coating is an ideal non catalytic media for purified Cu 70 Ni 30 alloy melts due to its small contact angle between the melt and coating layer. Considering that various microstructures form under different undercoolings, two critical undercoolings, Δ T 1 and Δ T 2, and their corresponding microstructures of Cu 70 Ni 30 alloy are well defined. Moreover, it is found that the manned trigging solidification in the non catalytic coating mould could be used to get directional undercooling dendrite structure while the melt undercooling is larger than the critical undercooling Δ T 2. A new concept of undercooling heredity is developed to evaluate the undercooling ability in a non-catalytic nucleation coated mold, where alloy melts were highly undercooled previously. Before the heredity experiment a non catalytic nucleation composite glass lined coating (BF) was prepared on the inner surface of mold and the Cu 70 Ni 30 alloy was selected to perform undercooling experiment in the BF non-catalytic coating mold. Its ratio of undercooling heredity was 0.76. The results prove that the BF coating is an ideal non-catalytic media for purified Cu 70 Ni 30 alloy melts due to its small contact angle between the melt and coating layers. Considering that various microstructures form under different undercoolings, two critical undercoolings, ΔT 1 and ΔT 2, and their corresponding microstructures of Cu 70 Ni 30 alloy are well defined. Moreover, it is found that the manned trigging solidification in the non catalytic coa ting mold could be used to get directional undercooling dendrite structure while the melt undercooling is larger than the critical undercooling ΔT 2.