Cylindrical vector beam has the characteristics of axially symmetric polarization and intensity distribution.Under strong focusing conditions,it will form a unique and strong local longitudinal electric field,so has unique application advantages in industrial processing,material handling,particle manipulation,optical microscopy and other fields.The mode selection coupler is the key device to realize the all fiber mode conversion.It has the advantages of simple structure,small size,high conversion efficiency,high mode purity and excellent fiber compatibility.Therefore,it can be said that the mode selective coupler is currently the most promising technical solution to obtain stable and reliable all fiber laser with cylindrical vortex beam output.Finally,the LP11 mode output with high mode purity and high stability is obtained experimentally by building a narrow linewidth all fiber laser with cylindrical vortex beam output.