We present four new transits of the planetary system TrES-3 observed between 2009 May and 2010 June. Among those, the third transit by itself indicates possible evidence for brightness disturbance, which could originate from a starspot or an overlapping double transit. A total of 107 transit times, including our measurements, were used to determine the improved ephemeris with a transit epoch of $2454185.910950pm0.000073$ HJED (Heliocentric Julian Ephemeris Date) and an orbital period of $1.30618698pm0.00000016$ d. We analyzed the transit light curves using the JKTEBOP code and adopting the quadratic limb-darkening law. In order to derive the physical properties of the TrES-3 system, the transit parameters are combined with the empirical relations from eclipsing binary stars and stellar evolutionary models, respectively. The stellar mass and radius obtained from a calibration using $T_{eff}$, log $ ho$ and [Fe/H] are in good agreement with those from the isochrone analysis within the uncertainties. We found that the exoplanet TrES-3b has a mass of $1.93pm0.07;M_{Jup}$, a radius of $1.30pm0.04;R_{Jup}$, a surface gravity of $28.2pm1.1;m;s^{-1}$, a density of $0.82pm0.06; ho_{Jup}$, and an equilibrium temperature of $1641pm23K$.