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We developed a model for in-situ wafer curvature values of AlInN/GaN distributed Bragg reflectors (DBRs) and determined InN mole fractions in the DBRs with the model. In order to develop the model, we experimentally investigated contributions of substrate temperature ramping and a GaN growth to changes in the in-situ curvature values during the AlInN/GaN DBR growth. We found that an increase of curvature changes at the substrate temperature ramping steps was explained by an increase of the total epitaxial layer thicknesses. Another finding was that strain in the GaN layers at the GaN layer growth steps was almost zero. Finally, we determined the InN mole fractions in the AlInN layers by using the model, showing excellent agreements with the values estimated from ex-situ X-ray diffraction measurements. The model reveals not only the entire in-situ curvature change profile but also the InN mole fraction under the precisely lattice-matched condition of AlInN/GaN DBRs.