The invention provides a double-grade compound swirl nozzle for a gaseous fuel low-pollution combustion chamber comprising an on-duty-grade swirler 1, a main-combustion-grade swirler 2, a simplified flame tube 3, a diffuser 4, a stabilized flame 5, a main swirl 6 and a wall-attached jet flow 7. The on-duty-grade swirler 1 and the main-combustion-grade swirler 2 mutually act to form the stabilizedflame 5, so that a detached flame is then formed; the mixing and ignition effect of an on-duty-grade high-equivalence-ratio combustion product and a main-combustion-grade fresh fuel gas is improved, the temperature of a main combustion area and the length of the flame are lowered, the standing time of the flame is shortened, and therefore the low emission purpose is achieved; the work range is widened and stabilized, the selectable types of fuel are increased, and the backfire problem, the carbon deposition problem and the like are avoided. The low-temperature wall-attached jet flow 7 providesa natural thermal barrier layer, so that the wall face of the simplified flame tube 3 is kept at a low temperature, design of a floating wall and other complicated cooling structures are basically avoided, the weight of the simplified flame tube 3 is reduced, the complexity of design is lowered, the strength of the simplified flame tube 3 is improved, and the protective effect is better.