The molten salt with KAlF₄ as the basic composition can not only be used as the electrolyte in the new low temperature aluminum electrolysis industry, but also be used as flux in the brazing of all kinds of aluminum radiators. Due to its low melt viscosity, low surface tension, super fluidity and high corrosion, the quantitative analysis of molten salt microstructure in this system has always been a high technical bottleneck. In order to study the microstructure of KAlF₄ melt, Raman peak and relative Raman scattering cross−section of [Al₂F₇]⁻ ion clusters in KAlF₄ melt were studied by means of in situ Raman spectroscopy and quantum chemistry ab initio calculation method. The [Al₂F₇]⁻ ion was quantitatively analyzed by the Raman spectrum analysis of KAlF₄ melt. The results show that in addition to K⁺, [AlF₆]³⁻, [AlF₅]²⁻and [AlF₄]⁻ ion clusters, 

there are also [Al₂F₇]⁻ ion clusters in KAlF₄ melt, and the content is about 1.75 mol%.