We measured the nuclear quadrupole resonance (NQR) of the solid solutions of NaClO3-KClO3 in the range of concentrations from 0 to 100% molar of KClO3 in (NaClO3 + + KClO3). The thermal diagram of the measured samples showed, that the solubility of the components in each other is limited. It is shown that up to 88·6% molar of KlCO3 it is possible to identify signals at a frequency which almost exactly corresponds to the NQR frequency of NaClO3, from this concentration the signals belong to the NQR frequency of KClO3. At the same time the width of the line shows anomalies in samples containing up to 10% KClO3 or up to 10% NaClO3. Broadening of the NQR line to the value 35 kHz in this region was interpreted as a result of prevalence of the “size-effect”, when the solid solution consists of a mixed crystal of one of the components with such a number of cations of the other component, which is sufficient to produce a chaotic order around the resonanting Cl35 nucleus and such alterations of the electrical field gradient, that they will widen the line.