The organoleptic properties of peach, as fruit in general, largely depend on the accumulated sugars and acids. From sucrose, glucose and fructose, main sugars found in peach, fructose is the sweetest one. While commercial peach has equivalent fructose and glucose concentration, some wild or ornamental accessions display an imbalanced fructose-to-glucose ratio with a very low fructose concentration. In addition to genetic control, sugar metabolism is driven by fruit development and environment. The relative role of biochemical strengths and gene regulation in the elaboration of fruit sugar content at maturity is not well known. As the complex interplay between synthesis, degradation, transport and storage held in the cell is difficult to formulate, mathematical modelling appears to be an effective tool to challenge the issue. Thus, on the basis of profiling data, we developed a kinetic model of sugar metabolism in peach fruit. It simulates the evolution of sucrose, glucose, fructose and sorbitol concentrations during fruit development. A particular attention has been given to represent cellular compartmentation (cytosol and vacuole) in order to modulate the availability of the metabolites for the enzymatic reactions. The model was parameterized for different peach genotypes including a particular phenotype with low fructose-to-glucose ratio. It described well genetic variability. It was then used to further explore the system including the mechanisms driving genotypic differences.