To determine the compounding of concrete beforehand by reduced trial kneading.

This concrete compounding planning system is provided with a water/mortar ratio operating means 1 for operating a water/mortar ratio based on each slump value on reference to compounding, a slump value estimating means 2 for calculating a regression line of the water/mortar ratio and the slump value and shifting the maximum slump value by a preset value at this time to calculate a regression line to estimate the slump value based on the regression line and a compounding judging means 3 for calculating the coefficient of correlation from the dispersion diagram of the slump value estimated by the slump value estimating means 2 and judging whether compounding is proper corresponding to whether the coefficient of correlation is a predetermined value or above. By this constitution, it can be diagnosed that planned compounding is proper or not before the trial kneading of concrete and the number of times of trial kneading can be reduced and the enhancement of quality becomes possible.