how to pronounced the word は?

When I check with the Hiragana, は this word should be pronounced as "ha",
but why it's pronounced as "wa" when it's in the sentence 私の名前はY u r i です ?

AJ,

Explained here...
http://en.wikipedia.org/wiki/Japanese_particles#wa

Look at the particles "e" and "o", too, while you're there.

Until WW2 kana orthography was very different from pronunciation (just like English spelling is sometimes very different from pronunciation).

http://en.wikipedia.org/wiki/Historical_kana_usage

For example, a word for "pity" was spelled "あはれ" ("ahare") but pronounced "aware", i.e. は was pronounced "wa".

After the war kana orthography was revised to be more phonetic.

http://en.wikipedia.org/wiki/Gendai_Kanazukai

However, there are some exceptions left based on traditional orthography, including particles は, を and へ.

Note that it also applies to こんにちは and こんばんは since they are derived from 今日は... (Today is ...) and 今晩は... (Tonight is ...) respectively.