Terahertz (THz) detector work at room temperature could greatly expand the application of THz science and technology. Ultra-thin(10μm)lithium tantalate crystal (LiTaO3) material was used as sensitive layer of the detector. The responsivity could reach up to 8.38×104V/W and the noise equivalent power (NEP) could be as low as 1.26×10-10W at 20Hz operating frequency by laser radiation source at 2.52 THz. Furthermore, this processing method to fabricate the ultra-thin LiTaO3 crystal material could potentially provide a feasible approach for even higher response terahertz detectors.