Active Galactic Nuclei (AGNs) are extragalactic objects characterized by extremely complex physical processes and strong temporal flux variability over almost the whole electromagnetic spectrum, which play a very important role in studying the formation and evolution of galaxies, cosmology and many other astrophysical problems. Flux variability is one of the most remarkable observational characteristics of AGNs and the variability time scales are from minutes to dozens of years. Multi-wavelength flux monitoring is the main means to study the nature of AGN flux variability.

In order to systematically study the total flux variability of AGNs in radio band, we launched a long-term program, which is called the quasi- Simultaneous Multiwavelength Monitoring of AGNs with the Nanshan 26-m radio telescope of Xinjiang Astronomical Observatory (XAO), namely SMMAN program. The monitoring data were acquired monthly with the cross-scan mode at C-band (4.8 GHz) and K-band (23.6 GHz) for a sample of about 100 AGNs selected from Fermi-LAT suvery.
Additionally, we also conducted weekly monitoring observations or Intra-Day Vairibility (IDV) observations for some of flaring Blazars to reveal their more complex variability time scales.