  As a Goldstone boson with zero quantum number and zero SM charge, the decays
of long-lived $\eta$ ($\eta^{\prime}$) meson provide a unique window to search
new physics beyond the standard model and new sources of CP violation, to test
the low-energy QCD theory, and to measure the fundamental parameters of light
quarks. For such goals in the physics frontiers we discuss a plan of building a
super $\eta$ factory at HIAF high-energy terminal or at CiADS after upgrade.
The high-intensity proton beam at HIAF provides a great opportunity of
producing a huge number of $\eta$ samples of more than $10^{13}$ events per
year, with multiple layers of thin targets of light nucleus. The physics goals,
the first-version conceptual design of the spectrometer, and the preliminary
simulation results are present.
