A demountable continuous shear connection is proposed to improve the reusability of steel-concrete composite beams and promote the development of a circular economy in construction. Unlike traditional welded shear studs and bolted shear connections, this continuous shear connection is comprised of a steel bar with discrete shear keys, thereby effectively reducing the workload of installing individual shear connections on construction sites. Furthermore, both the concrete slab and the steel beam can be simply dismantled and reused after sliding the continuous shear connection out of the steel beam. To study the interaction between these parts, elemental shear tests were firstly conducted. By studying steel plates of different thicknesses and grades, the expected connection shear fracture failure was observed. Subsequently, horizontal pushout tests were also implemented, by which the effects of the steel plate grade, thickness and the number of shear keys in each connection on the structural behaviour of composite beams were comprehensively explored. Results of tests indicated that the shear capacity of the connection was not significantly impaired as the number of shear keys increases. Under the ultimate load, the deformation of the embedded plates made of high-strength steel is greatly eased compared with those made of normal-strength steel. Because a large contact area was created between the embedded plate and surrounding concrete, premature concrete crushing observed in bolted shear connection cases was greatly improved. As a result, the application of the demountable continuous shear connection can significantly extend the service life of steel-concrete composite beams, thereby providing huge potential for reuse.