Phase　locking　of　a　diode　laser　array　in　an　external　Talbot　cavity　was　studied.　Far　field　distributions　of　in-phase　mode　and　out-of-phase　mode　were　calculated　using　Fresnel　diffraction　formula　of　one-dimension　on　the　basis　of　near　field　amplitude　distribution.　According　to　the　distributions　of　the　in-phase　mode　and　out-of-phase　mode　in　fraction　Talbot　cavity,　a　tilted　external　cavity　mirror　of　1/2　Talbot　cavity　was　adopted,　which　made　the　in-phase　mode　be　selected　and　the　loss　of　the　mode　be　lowered.　In　order　to　let　the　feedback　light　be　injected　into　the　elements　effectively　in　this　experiment,　a　sandwich　construction　of　composite　diamond　is　utilized　to　package　the　diode　laser　array　which　has　obviously　eliminated　the　smile　effect.　Phase　locking　of　in-phase　mode　is　obtained　in　the　experiment,　and　the　FWHM　of　the　single　lobe　is　0.11　mm.