How can i add string type column as a measure

How can i add Fact table string type column as a measure.

What are you looking to do with the string?

Measures are usually numbers that can be summed (or some other additive/semi-additive function). If you have string datatypes in your fact table, and you're not just looking for a count, are those string values unique per row? If so, what you'll want to build is a degenerate dimension. If not, you'll want to pull that out into a separate dimension table and foreign key to it with an int surrogate key.

Search for the phrase "degenerate dimension" in the following paper:

http://msdn2.microsoft.com/en-us/library/ms345125(SQL.90).aspx

(Don't use ROLAP like he suggests unless MOLAP just doesn't work for you.)