The paper proposes a decoy-state method to enhance the security of the Bennett-Brassard 1984 (BB84) Quantum Key Distribution (QKD) protocol in the presence of high loss. The method involves a legitimate user randomly replacing signal pulses with multi-photon pulses (decoy-states) and checking the loss of these decoy-states. If the loss of decoy-states is abnormally lower than that of signal pulses, the protocol is aborted. Otherwise, the loss of signal multi-photon pulses is estimated based on the loss of decoy-states, assuming they have similar values. The paper justifies this assumption and derives a security condition for the proposed protocol. The method is particularly useful for surface-to-satellite QKD, which suffers from high loss due to atmospheric conditions. The analysis shows that the decoy-state method can tolerate higher losses compared to traditional protocols, making it a promising solution for global secure communication.The paper proposes a decoy-state method to enhance the security of the Bennett-Brassard 1984 (BB84) Quantum Key Distribution (QKD) protocol in the presence of high loss. The method involves a legitimate user randomly replacing signal pulses with multi-photon pulses (decoy-states) and checking the loss of these decoy-states. If the loss of decoy-states is abnormally lower than that of signal pulses, the protocol is aborted. Otherwise, the loss of signal multi-photon pulses is estimated based on the loss of decoy-states, assuming they have similar values. The paper justifies this assumption and derives a security condition for the proposed protocol. The method is particularly useful for surface-to-satellite QKD, which suffers from high loss due to atmospheric conditions. The analysis shows that the decoy-state method can tolerate higher losses compared to traditional protocols, making it a promising solution for global secure communication.