Transient absorption spectroscopy using soft X-ray coherent light sources as ultrafast probes holds significant promise for applications in chemistry, biology, and materials science. This article presents the design of a transient absorption apparatus based on tabletop soft X-ray light sources. A commercial femtosecond laser system (4.4mJ, 25fs, 800nm, 1kHz) drives an optical parametric amplifier, generating a 900μJ, 28fs, 1440nm short-wavelength infrared (SWIR) pulse. This SWIR pulse is spectrally broadened and temporally compressed into a few-cycle pulse (400μJ, 16.5fs, 1530nm) via a hollow-core fiber compressor. The few-cycle SWIR pulse then drives the generation of attosecond soft X-ray high-harmonic radiation, with the maximum photon energy extending into the water window region (>300eV). The spectral resolution of the soft X-ray spectrometer is determined to be 334meV at 243eV. The remaining 800nm pump pulse from the OPA system is combined with the high-harmonic soft X-ray probe using a hole mirror, forming a Mach-Zehnder interferometer with a time jitter of <10fs over one hour of data acquisition. This setup demonstrates the feasibility of performing time-resolved soft X-ray spectroscopy in a compact experimental configuration. Preliminary studies of transient absorption near the argon L-edge and carbon K-edge were conducted, establishing this system as a powerful tool for element-specific, time-resolved, and transition-channel-resolved investigations of electron dynamics.