The invention provides a composite rear earth pyrochlore-type oxide catalyst for catalyzing burning for removing soot of a diesel vehicle and a preparation method thereof, belonging to the technical field of a tail gas cleaning catalyst of the diesel vehicle. The expression formula of the composite metal oxide is A2B2-xMxO7, wherein A is La, B is Sn, M is Mn, Fe, Co, Ni or Cu. The invention adopts a coprecipitation method to prepare the catalyst, the preparation process is simple, and the cost is low. The preparation method comprises the following steps: mixing metal nitrate and tin tetrachloride solution; adjusting the pH value by ammonia solution; drying the obtained deposit; and roasting the deposit at the high temperature to obtain the composite rear earth pyrochlore-type oxide catalyst. Under the effect of the catalyst, a simulation diesel vehicle exhausts, the burning temperature of the soot particles is lowered to the exhaust range of the diesel vehicle, and the speed of the soot oxidation rate is improved. The catalyst is a useful catalyst for removing the pollution of soot particles of the diesel vehicle.