I've moved your post to the correct forum so our members can try to help you...
We will need a little more inforation on it...
what type of orchid are you talking about in this post?
We also have a forum where you can introduce yourself and tell us a bit about what you are growing. It's called the Introductions - Break The Ice It's not necessary but your new friends would like to greet you properly
Ya Ya, If you could also include some pics, it would help.
Are you asking about what you believe to be normal flower loss or are you concerned about some negative condition? If you have been expecting this loss, wait until the plant has drawn the life back out of the flower stem and then cut it off. Take some cinnamon and apply it to the open cut. Avoid getting any on the roots.
Then sit back and enjoy the hundreds of pics you have of your blooming orchid until it blooms again.
Some might suggest cutting the green stalk off now, I like to wait. The plant will make good use of the flesh inside.
Don't forget to sterilize your cutting tools before and after. I use rubbing alcohol.