1

February is not a very good time to go to Safranbolu.There will be thick snow and it'll be very cold at that time.You can look around at the old Ottoman houses but it won't be very nice in that tyoe of weather.There should still be some hotels and pensions open but you need to contact them to be sure.
There are no trains only buses,Ulusoy Turizm and Metro Turizm cover the route and it takes 7 hours.
Maybe think about forgetting it this time and come back in spring summer or autumn when it would be more enjoyable.

2

thanks for your comment, i will have total 9days in turkey (start from istanbul) early of feb, i traveled some places in west coast before - do you have any suggestion for me, i am not sure how to plan during this season. thanks.

3

You could easily use all 9 days just in Istanbul but if you have already been there then I guess you may want to see other parts of the country.
Have you been to Cappadocia?If not then go there for 3 days.There will be snow there too but this is a place where the snow is not such a problem and it looks beautiful under snow!If your budget allows you could take a hot air balloon tour one morning too.So long as you are wrapped up warmly then it would be a good place to go to.
In February,with the exception of some parts of the Aegean coast and the southern Med. coast you are likely to find snow most everywhere.
There are overnight buses from Istanbul to Göreme with Nevşehirliler Seyahat and Metro Turizm bus companies and there are flights to both Nevşehir and Kayseri airports which are often quite cheaply priced.Check out Turkish Airlines and Pegasus Airlines.

4

thanks for your information :)