Making use of three dimensional (3-D) orthonormal bases of Haar wavelet functions, a 3-D multiresolution analysis is derived. This procedure is similar to the finite difference time domain (FDTD) method. While the proposed technique is applied to a realistic microwave passive component (microstrip low pass filter), the computational time is reduced approximately by half compared to the FDTD method and the result agrees well with traditional FDTD method.