A　high　average　power　and　high　beam　quality　nanosecond　laser　is　presented　that　is　based　on　CW　diode　side-pumped　Nd:YVO4　grazing-incidence　slab　amplifier.　A　TEM00,　passively　Q-switched　diode-pumped　Nd:YAG　laser　as　the　seed　laser,　generating　a　M-2　approximate　to　1.3　beam　train　of　0.25W,　2.3ns　pulses　with　adjustable　repetition　rate　in　the　range　5-20kHz.　After　double-pass　amplification,　more　than　20W　of　output　power　with　a　beam　quality　of　M-2　approximate　to　1.4　is　obtained　at　an　optical-optical　efficiency　of　35%.　The　high　brightness　of　this　laser　system　seems　ideal　for　nonlinear　optics　and　laser　processing　applications.