The 'Titanic' star was given the title for having 'a classic English rose complexion without needing lots of make-up to look stunning', reports the Sun.
Legendary actress Audrey Hepburn came second in the survey of 3,000 men and women.
Kelly Brook landed the third spot while Cheryl Cole came fourth.
Angelina Jolie was fifth followed by Scarlett Johansson.
The Ultimate Natural Beauties are:
1. Kate Winslet
2. Audrey Hepburn
3. Kelly Brook
4. Cheryl Cole
5. Angelina Jolie
6. Scarlett Johansson