I have a 98's chevy blazer, recently I found the driver-side floor is always wet after rain.
It has caused the carpet stained.
I was wondering what the problem is, how bad it could be, and how to fix it.

Thanks

 

check the driver's door seal. when i got my '97 the passenger door seal was leaking. with a little investigation i found that someone had splashed soda on the seal, and the sticky mess was preventing the seal from doing its job. cleaned it off and it hasn't leaked since.

 

Also, if the seals look like they are functioning properly, the next thing to check would be the weather seal behind the door panel. There are drain holes in the bottoms of the doors. If these drains get restricted with dirt/debris and then water builds up. If the weather deflector isn't sealed all the way around properly, it can allow water to enter into the passenger compartment.

Now I haven't heard of this in our trucks, but other GM vehicles seem to have this issue.

Another thing to ask is if you have a sunroof...?

 

yeah it happens Kyle...I have had thos problem off and on over the last two years....the year after I got my blazer...my passenger rear floor was so soaked..I had standing water...in the winter it froze...I checked the seals everything..the only thing I didn't do was pull up the carpet...(too lazy) the problem has for the most part fixed itself....sometimes it gets a little damp...but nearly as bad as it used to...I still have a pretty good idea it is my door seals....but alas I am a lazy blazer owner.....

 

You could always lie on the floor with a flashlight and rig your garden hose with a shower nozzle pointing at that corner of the truck. That should show you if the leak is at the door or the corner of the windshield.