Abstract
Qatar-1b is a transiting exoplanet which was claimed with possible transit timing variation (TTV) in this system. We have obtained ten light curves from our observations using the Palomar Observatory and the Crimean Astrophysical Observatory, combined with the public data in literatures, there are 40 light curves in total. Transit Analysis Package (TAP) is a package we use to get refined system parameters and uncertainties. The null TTV produces a fit with χ2red = 3.938. The residuals of linear fitting to mid- transit time of each transit infer there might be possible TTV. We have used three possible frequencies, 0.03881, 0.02998 and 0.00554, to fit sinusoidal function and the result of χ2red are 4.02, 3.643 and 4.047. Then we also check the false alarm probability of the frequencies, and it shows that there is no evidencd for periodic TTVs with a amplitude more than abou 25 seconds.