We report the generation of nanoseconds radiation at 177.3 nm with a maximum average power of 34.7 mW by second harmonic generation (SHG) in a 2.06-mm thick KBe(2)BO(3)F(2) (KBBF) crystal pumped with a homemade 4.2 W nanoseconds Nd: YAG laser at 355 nm operating at 10 KHz and 49 ns, which corresponds to an energy efficiency of approximately 0.826%. To our knowledge, it is the highest power generated at 177.3 nm. The dependence of phase matching angle of KBBF on temperature is presented for the first time. We also present the details on the measures for stable operation of a 4 mW nanosecond output at 177.3 nm with a lower pumping power in a thinner 1.37-mm KBBF crystal, and the stable output power is improved by about 20 times compared with previous results.