A broadband terahertz （THz） quasi-optical detector based on 3D-printed lens packaging has been presented， covering two typical atmospheric windows at 220 GHz and 340 GHz. The detector consists of an antenna-coupled detector chip and a 3D-printed lens. The chip was packaged on a multi-layer dielectric laminate， with a Schottky diode directly integrated across the feeding terminals of the on-chip antenna. The on-chip integrated broadband planar bowtie antenna was printed on a quartz substrate within the operation frequency range of 201-360 GHz， functioning as a radiator and a radio frequency （RF） choke. Bandwidth enhancement is achieved using a pair of capacitively loaded loops （CLLs） without increasing the antenna size. High-impedance folded low-frequency （LF） leads are incorporated to suppress high-frequency signal leakage. A lightweight， low-cost 3D-printed lens combined with an embedded metallized reflector enables unidirectional radiation and improved mechanical robustness. The detector achieves a maximum voltage responsivity of 2200 V/W over 200-230 GHz and 1885 V/W over 320-350 GHz. Measured radiation patterns agree well with simulations.