The utility model discloses a pig slaughtering marking device which comprises a seal seat, two built-in grooves are formed in the top end of the seal seat, the two sides of the inner walls of the two built-in grooves are connected with the two sides of corresponding seal clamps in a sliding mode, and two sets of strip-shaped penetrating grooves are symmetrically formed in the two sides of the bottom end of the seal seat. According to the pig slaughtering marking device, the two-way lead screw can drive the two seal clamps to move oppositely in the rotating process, number plates of different sizes are clamped and fixed, limiting clamping teeth and corresponding clamping racks are adjusted to move at the same time, the number plates of different sizes are clamped and fixed, and therefore the number plates of different sizes can be marked, and the number plates of different sizes can be marked. By means of the structure, number plates of different sizes can be clamped, different slaughter batches and management requirements are met, it is guaranteed that the number plates cannot be loosened or shifted in the clamping process, the accuracy and definition of marking are guaranteed, deviation or errors of the number plates in the marking process are avoided, and it is guaranteed that all marks are accurate.