The output properties of an external resonator SrWO4 Raman laser pumped by nanosecond pulses are studied. An actively Q-switched Nd∶YAG laser is used as the pumping source, with pulse width of 11.7 ns and energy of 80 mJ. The Raman laser cavity is a flat-flat one. Four output couplers with different reflectivities for the first- and second-Stokes wavelengths are used in the experiment. The relations between the output energy and pumping energy are measured, and the relations between the conversion efficiency and pumping energy are calculated. When the output coupler reflectivity for the first-Stokes wavelength is 39.9％, the obtained maximum output energy and conversion efficiency of the first-Stokes pulses are 23.9 mJ and 36.2%, respectively. When the output coupler reflectivities for the first and the second-Stokes wavelengths are 80.5％ and 12.4％, respectively, the obtained maximum output energy and conversion efficiency of the second-Stokes pulses are 16.4 mJ and 25.4%, respectively. The pulse widths of the typical first and second-Stokes pulses are 6.1 ns and 5.8 ns, respectively.