More and more applications of electrical resistivity tomography (ERT) for cylindrical objects have been rising in recent decades. This paper presents a 2.5-dimensional differential resistivity reconstruction scheme of cylindrical objects. The forward modeling algorithm incorporates the modified optimization wavenumbers to achieve an accurate 2.5-dimensional forward modeling. The modified optimization wavenumber selection is based on the approximate analytic solution of the circumference potential distribution of an infinitely long homogeneous cylindrical model, making it more accurate for cylindrical objects compared to the traditional optimization wavenumber selection which is only applicable for the half-space condition. In the laboratory, we measured the resistivity and resistance distributions of the sodium chloride solution-filled cylindrical tanks with/without a high resistivity rubber bar in the central. The modified and traditional optimization wavenumbers are included respectively to calculate the resistance distribution of the measured objects. The comparison results between the calculated and measured resistance distribution show that the modified optimization wavenumbers proposed in this paper can obtain higher calculation accuracy. The differential ERT incorporating the modified optimization wavenumbers is then employed to reconstruct the resistivity distribution of the cylindrical objects. The inversed resistivity values are in good agreement with the measured values. We, therefore, conclude that the modified optimization wavenumbers can result in better accuracy than the traditional one and the proposed 2.5-dimensional differential resistivity reconstruction scheme is time-saving and has great promise for the imaging of cylindrical objects.