I had applied for divorce and in the mean time I got married to another person. We have registered our marriage before I got my divorce decree.Now I want to change my spouse's name in passport and I could see that the documents such as my new marriage certificate and divorce certificate are required. My question is, as my re-marriage date is prior to the divorce decree date will it be considered as invalid?

Its illegal in most of the civilized world to get married to a second person while you are still legally married to another.

The second married won't just be "considered" illegal... its IS illegal.. and not valid.

Yes, as Smoothy has indicated, your second marriage is invalid (probably, but since we don't know where you are I will assume so). You should re-apply for a marriage license and, re-do the marriage ceremony.

Your spouse, not you, should appy to change the name on his/her passport.

Thank you for the response!