  AC-coupled Low Gain Avalanche Detector (AC-LGAD) is a new precise detector
technology developed in recent years. Based on the standard Low Gain Avalanche
Detector (LGAD) technology, AC-LGAD sensors can provide excellent timing
performance and spatial resolution. This paper presents the design and
performance of several prototype AC-LGAD strip sensors for the DarkSHINE
tracking system, as well as the electrical characteristics and spatial
resolution of the prototype sensors from two batches of wafers with different
$n^+$ dose.The range of spatial resolutions of 6.5$\mathrm{\mu m}$ $\sim$
8.2$\mathrm{\mu m}$ and 8.8$\mathrm{\mu m}$ $\sim$ 12.3$\mathrm{\mu m}$ are
achieved by the AC-LGAD sensors with 100$\mu m$ pitch size.
