Combustion system (10) for a gas turbine equipped with a premixing chamber (12) for air which is mixed with the fuel injected from a series of holes (11) creating a main central flame which is formed in a flame tube (14), the premixing chamber (12) is convergent towards a connection end with a combustion chamber comprising the flame tube (14), the combustion system (10) comprises a series of pilot devices (20) with premixing of the fuel gas, which create a series of corresponding pilot flames suitable for stabilizing the main central flame itself, at the same time reducing the polluting emissions.