I have try export my all products, its return only 6000 only products, actually in my site have 20,000 products are there.
1.Log into your Magento administrator area.
2.Go to System -> Import/Export -> Dataflow – Profiles -> Export All Products:
3.Under Profile Wizard -> Store choose the desired store where you will be exporting the products.
4.Under Data Transfer drop down menu choose Local/Remote Server.
5.Under Data Format make sure CSV / Tab Separated is selected for type and click Save Profile:
6.Open Run Profile tab and click Run Profile in Popup button:
7.This will save a file named export_all_products.csv under the var/export/ directory of your Magento installation. The export success screen will look like the following and will specify the file name where the products were exported:
8.Using an FTP client or CPanel File manager download this file to your local computer. You can edit it with a spreadsheet program (MS Excel, Open Office Spreadsheet) and add the products you would like to import:
9.Now we will show how to import the products.
10.Go to the Magento administrator area and choose System -> Import/Export -> Dataflow – Profiles -> Import All Products. Select the required settings in Profile Wizard tab:
11.Then choose Upload file tab and browse for the .csv file on your computer. Save changes:
12.Once you have uploaded it, click Import All Products, then Run Profile, select the .csv file you have just uploaded from the drop down menu and click Run Profile in Popup:
13.When import is completed, you will get an export success message