Deep‐ultraviolet nonlinear optical (DUV NLO) crystals are the key materials to extend the output range of solid‐state lasers to below 200 nm. The only practical material KBe2BO3F2 suffers high toxicity through beryllium and strong layered growth. Herein, we propose a beryllium‐free material design and synthesis strategy for DUV NLO materials. Introducing the (BO3F)4−, (BO2F2)3−, and (BOF3)2− groups in borates could break through the fixed 3D B–O network that would produce a larger birefringence without layering and simultaneously keep a short cutoff edge down to DUV. The theoretical and experimental studies on a series of fluorooxoborates confirm this strategy. Li2B6O9F2 is identified as a DUV NLO material with a large second harmonic generation efficiency (0.9×KDP) and a large predicted birefringence (0.07) without layering. This study provides a feasible way to break down the DUV wall for NLO materials. Be gone: A strategy to prepare a beryllium‐free material that does not grow in layers for deep‐UV (DUV) nonlinear optical (NLO) materials is developed and carried out. Introducing the (BO3F)4−, (BO2F2)3−, and (BOF3)2− groups in borates is a feasible way to balance the criteria of deep‐UV NLO materials, breaking down the DUV wall for NLO materials.