In this paper, a method of studying the three-dimensional (3-D) reluctivity tensor by measuring 3-D vector magnetic properties of the soft magnetic composite (SMC) material is presented. The magnetic flux density B and magnetic field strength H loci under alternating and rotating magnetizations are measured by using an improved 3-D tester. The magnetic reluctivity tensor can be expressed by a second-order three-dimensional full rank matrix by means of the experimental results. Taking the off-diagonal elements into account can benefit to accurate numerical analysis of magnetic field in 3-D flux electrical machines.