A technology for smelting and casting a C18150 alloy under the atmosphere condition comprises steps as follows: (1), furnace casting, baking and sintering: a basic refractory material is to be selected as a furnace liner material, acid refractory materials such as silica sand and the like cannot be utilized, and the operational process is as follows: furnace forging, furnace baking and sintering; (2), smelting and casting: a, baking of a covering agent, b, blending, c, smelting, d, casting, e, checking, f, sawing and g, warehousing. According to the technology for smelting and casting the C18150 alloy under the atmosphere condition, the problem of burning loss of Cr and Zr is solved fundamentally, meanwhile, melts are purified, consumption of raw materials is reduced, the production cost is greatly reduced, the ingot metallurgy quality is improved, the defects of pores, impurity inclusion, slag inclusion and the like caused by air absorption and oxygen absorption due to adoption of a traditional method for conveying molten metal by a launder are overcome, the ingot quality is improved, the technology further has the advantages of small occupied space, low labor intensity, low metal loss and the like, and low-cost production is realized truly.