Quantum digital signature (QDS) can guarantee the integrity and non-repudiation of messages with quantum mechanics-based information-theoretical security. Currently, most researches are concentrated on multi-decoy state QDS protocol. However, due to the existence of statistical fluctuations, the performance of multi-decoy state QDS systems could be deteriorated. In order to improve the performance of QDS, a 1-decoy state QDS protocol is proposed, and the corresponding security analysis and numerical simulation of its performance are also given. The signature rates with parameter optimization for 1-decoy state protocol and 2-decoy state protocol are compared through numerical simulation. It is shown that 1-decoy state protocol can improve the signature rate of the system a little under most transmission distance. In addition, 1-decoy state protocol is easier to be implemented, making it more practical and promising in possible digital signature scenarios.