Your question is a bit vague to me, but that might also be your English. There are basically two ways you can get content out of SDL Tridion, you either use the Core Service API (as Raj suggests), or you can use Content Porter and export the data you want (Content Porter will export it in a zip file, and in there you will find all the XML data from the items you exported).
Since SDL Tridion uses a structure of Pages and Components, you will need to restructure the data you get into what your target CMS will need yourself. That doesn't change from either of the options.
There is maybe a third option I could mention, and that is to scrape the content from the website which was published by SDL Tridion. Again this is all depending on what your target CMS requires as input for this migration, and depending on what migration tools you are using.
But that brings me to my last remark, it is a migration, and I know that developers tend to think "Automate" when they hear migration. I have written a blog post about migrations and my personal experiences once, and I came to the conclusion that you are most of the time better off hiring so called cheap labor and do the migration manually. That giives better results in the end, since you don't have to deal with possible faults in your exported data and can apply simple human logic (hey this link doesn't work anymore, let me try and find a replacement or remove it).
You can find my blog post here http://www.tridiondeveloper.com/how-to-say-goodbye-to-your-migration-tool