my file size is 37 mb including 3d objects. working fice but when I switch to layout AutoCAD get slower. its take long time... please guide how I can fast the layout switching. Thanks

37MB file?  Is that before or after cleaning up the drawing (i.e. - Overkill, -Purge, Audit and possibly WBlock)  What are your computer specs?

If you use 3D you will have a great interest in using as much as you can blocks to minimise the file size.I also have big 3D files with 38 pages of layout and it takes me some time to switch from one layout to an other ( and it takes me 2 minutes for each page to do a PDF file when I don't use publication ).When this happens I do a "beta" file with the same name + "a" at the end and with all the internal studies.My working file is without anything unnecessary for the layouts.Do you purge your files, do you use DGNPURGE ?

after cleaning the size is 37mb

OK aqeel222 then maybe the speed will only depend on the performances of your computer, this I'm not able to answer.I personally work in a big company and we don't choose our computer's characteristics.