Over the last few decades, the development of each new nonlinear optical (NLO)-active functional unit has led to the discoveries of a series of excellent NLO materials. In the present work, based on first-principles studies, we identified a novel deep-UV (DUV) NLO-active functional unit, a non-pconjugated group viz. (NH 2 SO 3) À. By combining alkalineearth metals with (NH 2 SO 3) À group, two DUV transparent NLO sulfamates, M(NH 2 SO 3) 2 (M = Sr, Ba) with superior optical properties including strong SHG responses (1.2 and 2.7 KH 2 PO 4 (KDP)), short UV cutoff edge (< 190 nm) and moderate birefringence (0.056@589.3 nm for Sr(NH 2 SO 3) 2) were successfully synthesized. Our work has provided not only two promising DUV transparent NLO crystals, but also an innovative non-p-conjugated unit for developing more DUV transparent NLO materials. Nonlinear optical (NLO) crystals that can produce deepultraviolet (DUV) coherent lights (wavelengths shorter than 200 nm) have been extensively applied to photolithography, semiconductor manufacturing, atto-second pulse generation and advanced instrument development. [1-6] For a long period of time, the exploration of DUV NLO crystals was mainly focused on the p-conjugated systems, such as borates, [7] carbonates [7] and nitrates, [7] which resulted in some excellent DUV NLO materials including KBe 2 BO 3 F 2 , [8, 9] b-Rb 2 Al 2 B 2 O 7 , [10] NH 4 B 4 O 6 F, [11] MB 5 O 7 F 3 (M = Ca, Sr), [12, 13] ABCO 3 F (A = K, Rb; B = Mg, Ca, Sr) [14-16] and M 2 (NO 3)-(OH) 3 (M = Sr, Ba). [17, 18] In 2014, Chen et al. reported the first DUV NLO phosphate, Ba 3 P 3 O 10 X (X = Cl, Br), [19] which opened a new avenue to the development of non-p-con