Tb(1-x)BO3:xEu(3+) (x = 0-1) microsphere phosphors have been successfully prepared by a simple hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as lifetimes were used to characterize the samples. The as-obtained phosphor samples present sphere-like agglomerates composed of nanosheets with highly crystallinity in spite of the moderate reaction temperature of 200 degrees C. Under ultraviolet excitation into the 4f(8) -> 4f(7)5d transition of Tb3+ at 245 nm (or 284 nm) and low-voltage electron beams' excitation, TbBO3 samples show the characteristic emission of Tb3+ corresponding to D-5(4) -> F-7(6, 5, 4, 3) transitions; whereas TbBO3:Eu3+ samples mainly exhibit the characteristic emission of Eu3+ corresponding to D-5(0) -> F-7(0, 1, 2, 3, 4) transitions due to an efficient energy transfer occurs from Tb3+ to Eu3+. The increase of Eu3+ concentration leads to the increase of the energy-transfer efficiency from Tb3+ to Eu3+ but also enhances the probability of the interaction between neighboring Eu3+, which results in the concentration quenching. The PL color of TbBO3:xEu(3+) phosphors can be easily tuned from green, yellow, orange, to red-orange by changing the doping concentration (x) of Eu3+, making the materials have potential applications in fluorescent lamps for advertizing signs and other color display fields.