Abstract: The dispersion and refractive index inhomogeneity of film materials and error accumulation of layers thickness are all the factors that cause the half-wave hole for a harmonic beam splitter, among them the periodic error accumulation of layer thickness and sensitive layer error is the primary one. Furthermore, the stack structure is also related to the half-wave hole. With the aid of TFCALC the numerical calculations and theoretical analysis were performed. Measures are taken and a harmonic beam splitter was designed and fabricated. The half-wave hole was eliminated fundamentally. Both theoretical and experimental curves are given in this paper, which agree well with each other.