The invention discloses a composite additive capable of decreasing sludge incineration fine particulate matter generation amount and a using method thereof, and belongs to the technical field of sludge incineration treatment. The composite additive capable of decreasing the sludge incineration fine particulate matter generation amount is a mixture of quicklime and kieselguhr, and the mass ratio ofthe quicklime to the kieselguhr is (0.25-1): 1. The using method of the composite additive comprises the steps that the quicklime and the kieselguhr are mixed and added into dried sludge powder of which the particle size is 150-500 [mu]m, the quicklime, the kieselguhr and the sludge powder are incinerated together, the incineration temperature is 750-950 DEG C, the obtained fine particulate matter generation amount is obviously decreased, in addition, the quicklime can react with the kieselguhr under the high temperature condition, and calcium silicate with the adsorption performance is formed. In addition, the quicklime and the kieselguhr are rich reserves, low in price and convenient to transport and store, and the sludge incineration fine particulate matter control cost can be effectively reduced.