Optical metasurfaces, with their capability to flexibly control the optical field at the subwavelength scale, have emerged as an ideal platform for achieving high-quality factor (Q-factor) resonances and tunable chiral responses, which holds significant importance for advancing chiral photonic devices. This study proposes a tunable chiral germanium metasurface based on bound states in the continuum (BIC). The structure consists of periodically arranged square germanium nanopillars with double concave grooves, situated on a reflective cavity with a Bragg mirror, which is composed of alternating stacks of Si and SiO₂, forming a single-port system. First, the Q-factor and band structure near the Γ point were studied through eigenmode analysis, observing that the Q-value tends to infinity at the Γ point, exhibiting the characteristics of ideal symmetric protection BIC. By breaking the in-plane C₂ symmetry, the ideal BIC is transformed into a quasi-bound states in the continuum (q-BIC), thereby exciting resonance modes that support chiral responses. The far-field polarization states at δ=0 nm, δ=20 nm, and δ=35 nm were characterized, and through the analysis of topological charges in momentum space, it was revealed that the unique topological properties of the q-BIC originate from the intrinsic resonance of the metasurface. To investigate the chiral response, the adjustment of the asymmetric parameter δ enabled the co-optimization of ultra-high Q-factor (Q=6121.14) and strong circular dichroism (CD=-0.94) responses in the near-infrared band. This demonstrates the feasibility of integrating high Q-factor and significant chirality in a single structure. Further utilization of the center spacing Δd of the double concave grooves achieved the inversion of the CD sign, providing a clear theoretical mechanism for the controllable design of chiral states. Multipole scattering power analysis reveals that the magnetic dipole plays a dominant role in the chiral q-BIC mode. In addition, by introducing a graphene layer onto the structural surface and modulating the Fermi level to alter material loss and dispersion, a significant tuning of the CD value was achieved within the range of -0.230 to -0.952 (tuning depth 0.722), thereby expanding the application potential of tunable chiral devices. This research provides a novel approach for developing high-performance, controllable chiral photonic devices. The proposed structure combines the strong field localization capability brought by high Q-factor, as well as chiral flexibility that can be achieved through geometric parameters and electrical tuning, demonstrating significant application potential in the field of chiral optoelectronic devices.