Mixed-alkali-metal hydroisocyanurate nonlinear-optical crystal RbLi(HC3N3O3)center dot 2H(2)O was grown by a facile aqueous solution method. It exhibits a short phase-matching wavelength (lambda(PM) = 239 nm) and a strong second-harmonic-generation response (d(eff) = 2.1KDP) benefitting from the well-aligned planar pi-conjugated (HC3N3O3)(2-) anions, as confirmed by the first-principles calculations. Moreover, solar blind ultraviolet radiation can be reached using the title crystal via a fourthharmonic-generation technique of a Nd-based laser, i.e., 1064 nm/4 = 266 nm.