An ultra-narrow spectroscopy of clock transition with high signal-to-noise ratio is crucial for a high-performance atomic optical clock.We present a detailed study about how to obtain a Hertz-level clock transition spectrum of~(171)Yb atoms.About 4 × 10~4 atoms are loaded into a one-dimensional optical lattice with a magic wavelength of 759 nm,and a long lifetime of 3 s is realized with the lattice power of 1 W.Through normalized shelving detection and spin polarization,~(171)Yb clock spectroscopy with a Fourier-limited linewidth of 5.9 Hz is obtained.Our work represents a key step toward an ytterbium optical clock with high frequency stability. An ultra-narrow spectroscopy of clock transition with high signal-to-noise ratio is crucial for a high-performance atomic optical clock. We present a detailed study about how to obtain a Hertz-level clock transition spectrum of (171) Yb atoms .About 4 × 10 ~ 4 atoms are loaded into a one-dimensional optical lattice with a magic wavelength of 759 nm, and a long lifetime of 3 s is realized with the lattice power of 1 W. Through normalized shelving detection and spin polarization, Yb clock spectroscopy with a Fourier-limited linewidth of 5.9 Hz is obtained. Our work represents a key step toward an ytterbium optical clock with high frequency stability.