In this paper, it is introduced briefly that the characteristic and classification of active galaxy nucleus (AGN) and blazar objects. We summarize the data processing of the Large Area Telescope (LAT) on the Fermi gamma-ray space telescope (Fermi), in detail. The most important work in this paper is that we summarized the analysis methods of variability of the blazars, and used these methods to analyze the variability of two blazars (3C 454.3 and Mrk421), which are FSRQ and BL Lac object, respectively. In order to analyze the variability characteristic of blazars quantitively , we achieved the variety curve of fluxes and spectral indexes in gamma-ray band (100MeV-300GeV). The result shows that both blazars have big outbursts in fluxes in the period, and the variety of flux is not related with spectral index, unlike the conclusions of earlier studies. Then, we also collected the data in both X-ray (15-150KeV) and radio (15GHz) bands, and achieved the lightcurves. Through analysing and comparing, we can find there exists a strong correlation between gamma and radio bands flux, with the variability in the gamma band leading radio band for both blazars. However, the X-ray flux is not correlated with them. In this paper, we discuss the possible explanations.
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