why he doesn't have and not he doesn't has?

One main verb (have) used in positive statements:

I have a pen.
You have a pen.
He has a pen.

In negative sentences, we must use the helping verb "do." This verb has the -es ending in 3rd person.
The main verb (have) does not change:

I do not have a pen.
You do not have a pen.
He does not have a pen.

thanks for replying .. bt my confusion has not yet gone!

When DO is used as an auxiliary, the main verb (in this case HAVE) is the bare infinitive.

i am not getting! pls explain me in layman language or little bit easy way pls

the question is why have is used here instead of has ? why he doesn't has the pen is not correct and then why have is used instead of has!

Anonymous my q is : he doesn't have a pen or he doesn't has a pen? i want to knw the difference that why we use doesn't have here in a simple language or u can say a little bit layman language. pls explain me the how and why

do, does, did, don't, doesn't and didn't must be followed by the verb form that is listed in the dictionary.

ha

Anonymouswhy he doesn't has the pen is not correct

You must study helping verbs.
The "helping verb" in your sentence is "do."
We use "do" like this:

I do
You do
He does
We do
They do

Do is a helping verb. In a sentence with "do", the main verb does not change.
"Do" changes.

I do go to

Pls explain the difference that why we use doesn't have