Hi all,

I use Lightroom, bridge, photoshop..

I create a tiff file which is panorama merge withe multiple sites, over 1g..but the whole laptop like very slow n I have to wait for hours.

I got 6g ram is not a lot but it isn't it not enough? It seems to me there is something abnormal which I can't figure it out.

 Check the performance in task manager if the 6gb memory is used up 100% there is your answer.

When the file is opened in LR and PS, then the 6GB is easily used up. PS hogs up memory. I have 8gb and its barely enough to deal with extremely large files.

And of course the processor needs to be able to deal with it too. I am using the intel i5

I'd keep the 1g file for when you get more ram or a faster computer.  Downsize it a bit and you should find it easier to edit.  Laptops usually don't have good graphics cards and that can slow it down with big image files.  I used to use a USB stick to boost ram but I'm not sure that made any difference.

adding a usb stick to your system does not increase the system memory, it is a storage device. Most laptops do not have good graphic cards. Even the I/O system of a laptop is slower than their desktop counterparts. 

If you are constantly creating PS files that are 1G and larger, I would suggest getting a good quad core
I7 or xeon workstation and put all the RAM that you can. Also get some fast 10k hard drives so you create a fast scratch disk. Do not use a external usb scratch disk if you want ultimate performance. USB cannot match the data transfer rate of of a internal sata drive. Get a graphics card with a co processor and a minimum of 1G of video memory.