High-precision transit observations provide excellent opportunities for characterizing the physical properties of exoplanetary systems. These physical properties supply many pieces of information for unvealing the internal structure, external atmosphere, and dynamical history of the planets. We present revised properties of the transiting systems WASP-35 and HAT-P-30/WASP-51 through analyzing newly available TESS photometry and ground-based observations obtained at the 1 m telescope of the Yunnan Observatories as well as from the literature. The improved system parameters are consistent with previous results. Furthermore, we find that the transits of HAT-P-30b/WASP-51b show possible timing variation that cannot be explained by a decaying orbit due to tidal dissipation and the Romer effect, while both apsidal precession and an additional perturbing body could reproduce this signal according to our comprehensive dynamical simulations. Because both systems are valuable targets that are suitable for transmission spectroscopy, we make some predictions for the atmospheric properties of WASP-35b and HAT-P-30b/WASP-51b based on the newly derived system parameters.