After I had finished my course , it run slowly. i tried to delete some of pictures and decrease the size of sound, but still slow. what can i do ?  

I have found several things to be helpful when trying reducing the size of the course (which might help with page load times).

Just before publishing a course I click Module>Delete Unused Files.

I've also found Audacity (free sound editing tool) to be a big help in manipulating sound files to make them smaller. I use .mp3 format audio files.

I do all my image editing outside of CourseLab. I use .png file format most of the time and make sure the images are exactly the size and shape I need before bringing them into Courselab.  

png is an exellent replacement for gif, for graphic pics such as most screendumps.
For photo's I would recommend jpeg though ...  

Assuming that you've optimised the pictures (for example don't use a 2048 x 2048 image then scale it down to 50 x 50) the speed should be reasonable.
The rate it renders depends on the speed your PC reads it off of the drive, the rate java works at and the browser render engine.
A fast PC will make it appear faster, sunject to the limitations of the browser engine.
I tried one module on some PCs at work,
(a)x8 3.3Gig cores, 4Gig DDR3 & nvidia Quadro FX3700
(b)x8 3.3Gig cores, 128gig RAM & quadro 3800.
So a fair bit of power to play with (we have some serious toys)these will read 256Gb of image data (8 images) and draw it on screen in under a second. It was plenty fast enough but still not 'instant' .. That's the java and browser engines slowing it down  

Thanks,
I tried my course on differnt pcs and labtop.
I kenow that it depends on pc speed
but i want to do my best to decrease time. Is there anyway ?  

Just optimise everything you can in the content sections. Pictures especially, always use a paint program (photoshop if you have the £/$ or GIMP if you have no money to spend) so they are the correct sizes.
Use native fonts, that is ones that are always available on a standard PC (arial, verdana etc).
Otherwise there isn't much you can do about it I'm afraid.  

Thanks, Nick