A dye Q-switched laser with nonlinear active multi-functional crystal NYAB is realized by using xenon flash lamp pumping for the first time. A 0.53μm pulse of 3 ns pulse duration and 1.28mJ energy (6MW/cm2 peak power) are obtained when small signal transmission of dye T0=0.3 and laser resonator length L= 10cm. Meanwhile, the relations between energy, pulse duration, and peak power of 0.53μm the laser pulse and L, T0 are measured. Moreover, the equations describing the mechanism of NYAB dye Q-switched laser in the case of L longer than rod length are derived. The theoretical results obtained by solving the equations are in agrreement with experimental results. In addtion, the ways of increasing the peak power of NYAB Q-switched laser are discussed.