The cash - raised by bring and buy sales across the UK - will go to villages in the African countries of Tanzania and Uganda.
It will provide clean, safe water for 30,000 people.
They hope to do this in three ways:
Put in pumps so clean water can be brought up from underground
- Pay for education so the villagers know about better hygiene
- Provide toilet kits so people can build their own loos
The target is £500,000, but Blue Peter appeals have a history of making even more than that.