End-pumped by a 970 nm diode laser, 1534 nm pulse laser with about 16 μJ energy, 48 ns duration, and 21 kHz repetition rate was obtained at absorbed pump power of 11.8 W in a Z-cut 1.08-mm-thick Er(3+):Yb(3+):Sr(3)Lu(2)(BO(3))(4) crystal passively Q-switched by a Co(2+):Mg(0.4)Al(2.4)O(4) crystal. The effects of absorbed pump power and resonator cavity length on output performances of the pulse laser were investigated. Compared with that of the Er(3+):Yb(3+):LuAl(3)(BO(3))(4) laser in a similar experimental condition, higher pulse energy realized in the Er(3+):Yb(3+):Sr(3)Lu(2)(BO(3))(4) crystal may be originated from its smaller stimulated-emission cross section at 1534 nm and longer fluorescence lifetime of the (4)I(13/2) upper laser level of Er(3+) ions.