Well, if we ignore the normal usage in Christianity, this is how you would say God is my savior...
shàng dì shì wǒ jiù zhǔ
When you are ready, you can order your tattoo template here:
http://www.orientaloutpost.com/chinese- ... ervice.php
I don't count articles, so just count this as 3 words for the purposes of pricing the templates. The total will be $30 for access to this phrase in over 100 styles.
I would still rather give you something like "Jesus Christ is my Savior."
However, I was talking to Protestant Chinese Christians, so there might be a Catholic tenet or idea that is different from the Protestant ideas. There have been Catholics in China since Jesuit missionaries ministered to the elite of China in the 16th century (and later the Jesuits learned that you should minister to everyone, including the common, lest the commoners rise up in resentment and chase you out of the country). There are many Catholic churches across China today, however, I don't think I personally know a Chinese Catholic to check any information with.
I can test the phrase by doing a Google search with quotes:
"上帝是我救主" (God is My Savior) gets just 3 results.
"耶穌是我救主" (Jesus is My Savior) gets 13,400 results.
"耶穌基督是我救主" (Jesus Christ is My Savior) gets 16,300 results.
While not completely scientific, this does show how much more often the Jesus phrase is used in the Chinese-speaking Christian world.
I am putting all of this extra effort into this, just to make sure you are making an informed decision (and not get a tattoo that you will regret later).