This paper aims to examine baes metal alloy in all its aspects - the roles of elements, the content of every element according to uses, characters, laboratory technique methods and the kind of artificial base metal alloy registered in A.D.A. Specification. The results are as follows; 1. Base metal alloy is used widely bacaues it is rather cheap, but it should be handled appropriately in operating because its quality is bad. 2. Classifying base metal alloy, it is classified into Co-Cr alloy, Ni-Cr alloy, and Ni-Cr-Co alloy according to element, it is classified into partial denture alloy, surgical alloy and crown & bridge alloy according to use. 3. Among elements of base metal alloy, Bellium lowers the melting point of the alloy and increases the strength, but the amount should be limited when it is used because it destroys the organization of a living body. 4. The investments for base metal alloy are ethyl silcate bonded investment and phosphate bonded investment which endure well at high burn out temperature. 5. A.D.A specification No.14 in Kore contains Niranium, Nobilium, regalloy, Ticonium and Vitallium.