The invention relates to a first-stage selectivity hydrogenation method for pyrolysis gasoline fractions, which uses palladium series hydrogenation catalyst which is used after being reduced. The first-stage selectivity hydrogenation method for the pyrolysis gasoline fractions is characterized in that the hydrogenation technological conditions are as follows: the volume space velocity of a liquid is less than or equal to 5h<-1>, the inlet temperature of a reactor is between 28 and 120 DEG C, the reaction pressure is more than or equal to 2.4 MPa, and the hydrogen/oil volume ratio is between 50 and 500; the palladium series hydrogenation catalyst takes theta-type alumina or theta and alpha mixed crystal type alumina giving priority to theta type as a carrier, takes metallic palladium as an active ingredient, and contains 0.2 to 0.5 weight percent of the active ingredient-the palladium, 2 to 8 weight percent of auxiliary agent-lanthanum and/or cerium, and 2 to 8 weight percent of alkaline earth element as calculated by 100 weight percent of the catalyst; and the catalyst can still be used by regeneration after being subjected to coking and deactivation. Under the condition of the application method and the technological conditions, the catalyst has good hydrogenation performance, and particularly still has good hydrogenation activity and stability when hydrogenation raw materials contain trace water and colloids.