852nm　Narrow　linewidth　lasers　can　be　widely　used　in　the　field　of　ultra-fine　spectrum　measurement,　Cs　atomic　clock　control,　satellite　and　optical　fiber　communication　and　so　on.　Furthermore,　the　stability　of　the　single　lateral　mode　is　a　very　important　condition　to　guarantee　the　narrow　linewidth　lasers.　Here　we　investigate　experimentally　the　influence　of　the　narrow　ridge　structure　and　asymmetrical　waveguide　design　on　the　stability　single　lateral　mode　of　an　852nm　diode　laser.　According　to　the　waveguide　theoretical　analysis,　ridge　mesa　etch　depth　(Delta　n,　related　to　the　refractive　index　difference　of　parallel　to　the　junction)　and　ridge　mesa　width　(the　narrower　the　more　control　force　to　low　order　mode)　are　the　main　elements　for　lateral　modes.　In　this　paper,　we　designed　different　structures　to　investigate　and　verify　major　factors　for　lateral　mode　by　experiment,　and　to　confirm　our　thought.　Finally,　the　5　mu　m　mesa　ridge　laser,　800nm　etch　depth,　with　groove　structure　obtains　excellent　steady　single　lateral　mode　output　by　150mA　operating　current　and　30　degrees　temperature.　The　optical　spectrum　FWHM　is　0.5nm　and　side　mode　suppression　ratio　is　27dBm　with　uncoated.　The　laser　with　1mm　cavity　length　showed　the　threshold　current　of　50mA,　a　lasing　wavelength　of　lambda　=　852.6nm,　slope　efficiency　of　above　0.7mW/mA.　We　accomplished　single　lateral　mode　of　ridge　waveguide　edge-emitting　lasers　which　can　also　be　used　as　a　laser　source　in　the　ultra-narrow　linewidth　external　cavity　laser　system.