<p>On the basis of generalized Bell state of <i>d</i>-level quantum system, this paper proposes a novel lightweight mediated quantum key distribution protocol, allowing two restricted participants to establish a shared secret key with the help of a quantum server. The restricted participant only equips with limited quantum capabilities of performing generalized Hadamard operation and measuring single particle in computational basis, i.e., Z-basis, while the quantum server allowed to be dishonest only need prepare the generalized Bell states. Since only one-way quantum communication channel is adopted in the presented protocol, which makes it is automatic secure against to Trojan horse attack, security analysis illustrates that the presented protocol is immune to intercept-resend, measure-resend, and entangle-measure attacks. Comparisons show that both the quantum server and the restricted participant of presented the protocol require lesser quantum capabilities, and it also possesses higher key rate.</p>