1. INTRODUCTION
2. THE SAMPLE AND DATA
2.1. The AGN sample
2.2. X-ray data
2.3. Multi-band SED fitting and Mid-IR data
3. MID-IR EXCESS PRE-SELECTING CT AGNS
4. MULTI-WAVELENGTH DIAGNOSTICS
5. DISCUSSION
5.1. X-ray origin for CT AGNs
5.2. Why the $N_{H}$ is underestimated?
5.3. Selection efficiency of CT AGNs
5.4. Accretion of central BH of CT AGNs
5.5. The properties of CT AGN host galaxies
6. SUMMARY