The invention discloses a prefabricated reinforced concrete primary beam and secondary beam splicing joint and a construction method thereof. The prefabricated reinforced concrete primary beam and secondary beam splicing joint comprises a first splicing component and a second splicing component; the first splicing component comprises a pre-buried splicing component and an additional splicing steelplate corresponding to the pre-buried splicing component, the pre-buried splicing component comprises a pre-buried steel plate with a plurality of anchor ribs and T-shaped steel with bolt reserving holes, and the pre-buried steel plate and the T-shaped steel are welded into a whole; the additional splicing steel plate is a steel plate with bolt reserving holes and is connected with the T-shaped steel through bolts; and the second splicing component comprises a prefabricated concrete beam and an outward-extending steel reinforcement cage, and the outward-extending steel reinforcement cage is atruss-type steel reinforcement cage composed of longitudinal ribs, oblique supports and stirrups, wherein the ends of the longitudinal ribs are reinforced by equivalent bars.