The approaches of compressing the line width of pump source of DPAL(diode-pumped alkali vopor lasers) have been analyzed in this paper,including employment of holographic grating,volume Bragg grating and Fabry-Perot etalon in the Littrow structure.The setup of different ways have been analyzed and their results,advantages and disadvantages have been compared,providing scientific guidance to looking for a method which has a simple setup,efficient reduction of the line-width and the least power loss.