I want no if is only situps can help in reducing tummy

Short answer is no. Sit-up can help to strengthen the muscles in your tummy, but if those muscles are covered with a layer of fat, your tummy will still look fat.

The best way to get a tight tummy is to clean up your diet, cut out all the junk, fried and sugary foods. Do lots of exercise in general, so that you burn calories. Walking, running, cycling, climbing stairs, dancing, swimming etc.

For best results, do exercises that work your whole body, not just the tummy