Generally, a superconducting nanowire single-photon detector (SNSPD) is composed of wires with a typical width of $\sim 100\mathrm{nm}$. Recent studies have found that superconducting strips with a micrometer-scale width can also detect single photons. Compared with the SNSPD covering the same area, the superconducting microstrip single-photon detector (SMSPD) has smaller kinetic inductance, higher working current, and lower requirements in fabrication accuracy, providing potential applications in the development of ultralarge active area detectors. However, the study of SMSPD is still in its infancy, and the realization of its high-performance and practical use remains an open question. This study demonstrates a NbN SMSPD with a nearly saturated system detection efficiency (SDE) of $\sim 92.2\%$ at a dark count rate of $\sim 200\mathrm{cps}$, a polarization sensitivity of $\sim 1.03$, and a minimum timing jitter of $\sim 48\mathrm{ps}$ at the telecom wavelength of 1550 nm when coupled with a single-mode fiber and operated at 0.84 K. Furthermore, the detector’s SDE is over 70% when operated at a 2.1 K closed-cycle cryocooler.