Abstract: The representations of magneto-calorific power P for composite wire of magnetic core with conductive layer in various shapes (columnar, tubular and sheet) are derived. The results showed that the eddy calorific power can be divided into two parts. One is relative to magnetism, electricity and the size of sample, another is relative to the adapted structure of magnetic core and conductive layer (structure factor Ψ), and to sample shape (shape factor η).The analysis indicates that the thinner the covered conductive layer is^the greater the calorific power generated by the conductor gets.