I recently got Italian Study visa D type which is valid for a year. Now I got admission from German university and i am more interested in Germany. Can two student visas from EU countries issue at a same time? or German embassy ask me to cancel the italian visa first?
Yes, since a D-Visa/residence permit is specific to the country that issued it.
Depending on the jurasdiction, a D-Visa/residence permit may become invalid if you have abandoned your residence (in Germany after 6 months or you have deregistered your residence and left the country without the intention of returning).
It does not need to be specificly cancelled.
There are perfectly valid reasons to have more than one residence permit (own houses in 2 countries that you visit regularly), so in general one country will really not be interested in the other countries residence permit.