The invention discloses a highway engineering new and old pavement splicing structure and a construction method thereof, and belongs to the field of highway reconstruction and extension projects. Thenew and old pavement splicing structure comprises an original pavement and a new pavement, the new pavement sequentially comprises a cushion layer, a subbase layer, a base layer, a lower surface layer, a middle surface layer and an upper surface layer from bottom to top, and the upper surface layer is laid at the top of the middle surface layer and the top of the original pavement; non-fine macroporous concrete drainage belts are arranged at the splicing parts of the cushion layer and the subbase layer and the original pavement, and a cast-in-place concrete layer is arranged at the splicing part of the base layer and the original pavement; and reinforcing steel bars and reinforcing pieces are arranged between the cast-in-place concrete layer and the original pavement. The construction method of the new and old pavement splicing structure comprises the following steps of: S1, surveying and setting out; S2, milling an old road; S3, excavating steps; S4, constructing the cushion layer andthe subbase layer; S5, constructing the base layer; and S6, constructing an asphalt surface layer. The phenomena of deformation and differential settlement at the joint of new and old pavements are reduced, the common quality problem of longitudinal reflection cracks of the pavement is reduced, and the service life of the pavement is prolonged.