In this work, a sandwich-structured Pt-graphene-Pt (P-Gr-P) nanocomposite has been prepared by a two-step method including (i) a chemical and (ii) an electrochemical reduction process. The P-graphene oxide-P (P-GO-P) nanocomposite was firstly synthesized by an in situ growth method, during which platinum nanoparticles (PtNPs) grew on both sides of GO. In the second step, P-GO-P was coated onto a glass carbon electrode (GCE). In this process, GO in the P-GO-P nanocomposite was reduced to a more conductive form of graphene (Gr). The obtained sandwich-structured P-Gr-P can effectively separate the individual layers of Gr sheets from each other, prevent the agglomeration of Gr sheets and improve the conductivity of the Gr film. In addition, the electrocatalytic properties of the as-prepared P-Gr-P nanocomposite towards the oxidation of salbutamol (SAL) were investigated. Results revealed that the sandwich-structured P-Gr-P nanocomposite with higher electrochemically active surface area showed better electrocatalytic activity toward SAL oxidation than PtNPs-Gr prepared by using the one-step electrochemical co-deposition method. On the basis of the excellent electrochemical activity of the P-Gr-P nanocomposite, a highly sensitive electrochemical platform was developed for the rapid detection of SAL. The present work provides an interesting strategy to prepare a Gr-based nanocomposite for electrochemical sensors.