Composite materials have some obvious advantages such as high specific strength 、high specific modulus 、corrosion resistant 、abrasion resistant and so on, it is believed to be highly competitive compare to other materials. Advanced composite materials have been used more and more widely in defense industry, among them carbon fiber reinforced resin base composite material is most representative  ,there has great value for the study of carbon fiber composite materials. Eddy current is a nondestructive testing technology widely used on metal materials, the using of eddy current technology in aviation domain has a long history, but there is few reports on composite material with eddy current NDT. Experiments show that eddy current used on composite material is feasible, and the result is satisfactory. The thickness measurements of carbon fiber advanced composite materials have been done in two different ways.