In this thesis, efficient methods for estimating the electromagnetic properties of multiple wire-type scatterers are developed and validated. Firstly, we proposed the hybrid method combined the Foldy-Lax equation with the MoM under the assumption that identical scatterers have arbitrary directions. This method is geometry based method, and then it requires the exact position and orientation of wire-type scatterers. For verification, measurement models were fabricated and measured. Compared to the results of the measurement, the results of the proposed method showed good accuracy. Proposed hybrid method can be applicable to RCS calculation for not only wire scatterers but also multiple scatterers with any identical shape. For statistic based method, we propose the generalized equivalent (GEC) method which considers the multiple wire-type scatterers as an effective medium. The GEC method requires only the density and the orientation distribution (mean and standard deviation) of the wire scatterers are needed. In addition, the scattered wave is then calculated from this effective medium. Therefore, fast computation becomes possible for estimating electromagnetic properties of multiple wire-type scatterers. The proposed GEC method is verified through comparison with the effective permittivity by measurement and established references. We demonstrate that the GEC method achieves good accuracy with a very low computation burden. The proposed hybrid method and GEC method are applied to estimate the RCS of chaff cloud and electromagnetic properties of 2D fiber composites.