The main reason why the ppt file is too large is that pictures, videos and audio are inserted. (Pictures are the most common)

Method: compress the picture.

Lower version of office (2003, 2007): Select a picture-right click-format the picture-compress.

Office Advanced Edition (20 10, 20 13, 20 16): Select Picture-Format-Compress Picture.

You can choose to compress all the pictures in the selected picture or document, or you can choose the compression ratio.