We report the results of the broadband dielectric constant and loss tangent of the new complex perovskites Ba3MnTa2O9 with the test frequency f in different ranges from 1 kHz to 15 GHz. For the test frequency f below 1 MHz, the dielectric constant and loss tangent of the specimens were measured using a LCR meter with four-terminal configuration. The measurements at frequencies between 50 MHz and 1 GHz were performed by the lumped impedance method, which uses an impedance analyzer to measure the complex impedance of the specimen. At frequencies above 1 GHz, two samples with diameter 9 mm and different thicknesses (2.73 mm and 5.42 mm) were measured by a home-made Hakki-Coleman resonator. The TE011 resonant peaks were found and identified with an Agilent PNA net-work analyzer. The dielectric constants were found to remain almost constant with the test frequency at room temperature. The calculated values of the real part dielectric constants are 17.74 and 17.53 at 9.86 GHz and 15.43 GHz, respectively. The unloaded Q factors deduced from curve fitting of the peaks are both around 200.