The　effects　of　pulsed　laser　interaction　with　matter　have　become　a　center　for　research.　The　pulsed　laser　has　become　an　indispensable　manufacturing　tool　in　the　efficient　machining　of　polycrystalline　diamond　(PCD)　and　other　materials.　Herein,　the　ablation　threshold　and　chemical　modification　of　PCD　irradiated　using　ultraviolet　(UV)　nanosecond　laser　is　scrutinized.　Using　a　UV　nanosecond　laser　source,　a　bulk　of　PCD　is　ablated　in　air,　and　multipulse　processing　is　executed　at　a　wavelength　of　355　nm.　The　ablation　threshold　of　PCD　is　reported　to　be　approximate　to　3.7326　J　cm(-2)　based　on　the　linear　relationship　between　the　laser　pulse　energy　density　and　the　crater　diameter,　with　a　Gaussian　distribution　of　the　laser　intensity　on　the　cross-section.　Furthermore,　the　sp(3)　structure　transitioned　to　the　sp(2)　graphite　phase　when　the　PCD　is　exposed　to　UV　nanosecond　laser　irradiation.　Consequently,　this　study　provides　a　theoretical　and　experimental　reference　for　UV　nanosecond　laser　micromachining　of　PCD　materials　in　the　research　and　metal-working　industries.