We presented a new free space calibration technique for non-contact measurement of electromagnetic properties of nano-carbon composites. Compared to previous calibration methods, this technique is simple to use and can be applied in real time, in a variety of testing conditions. While other methods require multiple reference values and/or movement of antennas, this technique employs only two reference measurements. The first measurement is from a known conductor, such as aluminum metal plate. The second is from an air slab with geometrical propagation length equal to that of the specimen being tested. The reconstructed conductivity and permittivity agree favorably with the values obtained using the previously reported calibration techniques. The measurement results are illustrated on nano-carbon epoxy composites with inter-laminar multi-walled carbon-nanotube structures that can be either thicker or thinner than the skin penetration depth. Depending on the arrangement of the carbon nanotube networks structures, the electromagnetic properties of these laminates can be tailored to obtain specific microwave absorbing and reflecting characteristics.