A type antiferromagnet attention in recent years, popular at home and abroad, in particular, A type antiferromagnet MgB2. MgB2 has a simple chemical composition and crystal structure, material, low cost, high carrying capacity. And the finished product and processing properties of MgB2 good, so prevalent that it is possible in the near future become a Nb-Ti alloys with comparable practical superconducting materials, have significant applications. This paper discusses the use of AC magnetic susceptibility of superconductivity. First introduced the AC susceptibility and resistivity of the relationship. Of A-type antiferromagnet MgB2 samples of a number of super-conducting parameters, including the critical temperature Tc, upper critical field Hc2, the critical current density Jc, irreversibility field, etc. and the temperature T of the relationship between AC loss and the frequency and temperature T of the relationship. In addition, a brief description of the ac susceptibility in the magnetic flux dynamics and nonlinear nature of the research method. A class of anti-ferromagnetic model is ferromagnetic layer, and in the antiferromagnetic layer is ordered. A strong association with many types of anti-ferromagnetic material structure. In particular, people are very interested in the recent MgB2 superconducting materials. Therefore, the magnetic susceptibility of A type antiferromagnet is very meaningful.