Hi,which is better to reduce depression,,walking on treadmill or using elliptical..thank you very much?

Eithet one will help: Both are great forms of exercise. Either one may help reduce depression. I'm not aware of any studies differentiating the two with respect to their impact on depression.

Exercise: Exercise is a great place to channel mental stress and/or aggression. I would also submit that exercise releases the body's natural endorphins, that give feelings of well being and satiation, such as the tell-tale "runner's high." Try 20 minutes of walking briskly every day for a week, and see how the walking effects you.