A　passively　Q-switched　Nd:　YAG/Cr4+:　YAG　microchip　laser　with　a　low　time　jitter　and　a　high　repetition　rate　is　reported,　which　uses　a　single-tube　laser　diode　with　a　wavelength　of　808　nm　as　the　pumping　source.　Based　on　the　polarization　orientation　characteristic　of　a　Cr4+:　YAG　crystal　with　a　cutting　direction　of　[001]　at　a　certain　incident　beam　power　density,　the　polarized　pumping　method　is　chosen　to　make　the　polarization　direction　of　the　pumping　light　parallel　to　the　crystallographic　axis　direction　and　all　of　the　residual　pumping　light　after　absorption　by　the　Nd...YAG　crystal　is　used　for　bleaching　the　electric　dipoles　along　the　crystallographic　axis　direction　of　the　Cr4+:　YAG　crystal.　The　results　show　that　the　output　pulse　time　jitter　of　the　Nd:　YAG/Cr4+:　YAG　passively　Q-switched　microchip　laser　can　be　effectively　reduced　with　the　optimization　of　the　orientation　of　the　Cr4+:　YAG　crystal　with　a　cutting　direction　of　[001]　when　the　polarized　pumping　method　is　adopted.　©　2018,　Chinese　Lasers　Press.　All　right　reserved.