My 15 months daughter passes stool 3 times a day. She started this habit last week. Before that she had passed her stool like after 2 or 3 days and that was hard.
She is active, healthy every thing is normal.
Could anyone tell me is it normal?
Children passing stool on a variable basis is not uncommon, and not in and of itself a reason for concern normally. Often stool changes are due to eating habits; for example, a diet high in fiber (veggies/fruit) will yield softer, more frequent stools, while a diet primarily consisting of meats and cheeses will likely yield infrequent, hard stools.
Two to three times a day is still well within 'normal'; both of my (13mo and 33mo) children are in that range. Both are pretty good about veggie/whole fruit consumption, and thus have pretty soft stools. When they eat more meat/yogurt, they become less frequent and harder.
That said, this is not a site for medical advice, so if you have some concern, you should certainly talk to your pediatrician.