Both　spectral　and　pseudo⁃spectral　acceleration　play　an　important　role　in　the　seismic　design　of　structures.　However,　only　one　of　them　is　specified　in　most　seismic　codes.To　clarify　the　relationship　between　the　two　helps　to　obtain　another　spectrum　from　the　given　spectrum.Previous　research　on　the　relationship　between　Sa　and　PSa　are　mostly　confined　to　the　analysis　of　the　effects　of　structural　damping　ratio　and　period.Recent　studies　have　shown　that　magnitude,　epicentral　distance　and　site　class　also　have　an　effect　on　the　relationship　between　the　two.　In　this　paper,　the　effects　of　magnitude,　epicentral　distance　and　site　class　on　the　relationship　between　Sa　and　PSa　are　systematical⁃　ly　discussed　by　statistical　analysis　of　a　large　number　of　ground　motion　records（16　660　seismic　acceleration　time　histories）.　The　results　show　that（1）the　influence　of　magnitude　on　the　relationship　between　Sa　and　PSa　is　very　sig⁃　nificant,　and　the　difference　between　Sa　and　PSa　decreases　with　the　increase　of　magnitude；（2）The　effect　of　site　class　is　second　to　magnitude　and　is　related　to　magnitude.　The　influence　of　site　class　on　the　relationship　between　Sa　and　PSa　is　not　uniform　under　different　magnitudes.　（3）The　influence　of　epicentral　distance　on　the　relationship　be⁃　tween　Sa　and　PSa　is　very　small　and　can　be　ignored.Finally,　based　on　these　conclusions　and　through　nonlinear　re⁃　gression　analysis,　the　transformation　expression　of　Sa　and　PSa　considering　magnitude　and　site　class　is　established.　©　2022　Authors.　All　rights　reserved.