A method to control the combustion of an internal combustion engine, which comprises determining a combustion model, which provides a spark advance depending on an objective value of the rate of water to be injected, on the rotation speed, on the intake efficiency and on an open-loop contribution of a combustion index; calculating a first closed-loop contribution of the spark advance depending on the combustion index; calculating a second closed-loop contribution of the spark advance depending on a quantity indicating the knocking energy; and calculating the objective value of the spark advance angle to be operated through the sum of the spark advance value provided by the combustion model and of the first closed-loop contribution or, alternatively, of the second closed-loop contribution.