I have a beeman rs1 chinease air rifle is the trigger adjustable and if so How?

Yes they are adjustable, both 1st and 2nd stage and also trigger weight.
The trigger group is easily disassebled and honed with fine emery paper. You really dont need a mirror surface but the factory surface is very far from smooth. There are som sharp corners on the sear and the trigger lever, DO NOT ROUND THEM.
Pay close attention to the three small springs inside, if you get them mixed up the rifle will not lock.
This work will make all the difference in your rifle.
Just work slowly and with caution not to change the angles in the trigger geometry, all you want to do is polish the surface.

Tutorial can be found here http://webpages.charter.net/guru1/documents/RSE%20Airguns%20-%20Beeman%20RS2%20trigger%20guide.pdf

Those triggers are set at about 500 lbs, I think it is for safety reasons, there is no adj, and I wouldn't even attempt to take it apart, if you do, you might as well throw it in the trash now. A drop of oil on the sear might help it, but you will never get a smooth trigger out of it. You would have to get it apart, hone every part of the trigger group, and when you do, you will be loosing the only thing holding back that spring. I'm sure it could be done, But even I wouldn't want to mess with it, and I can take apart a jumbo jet. It might not go back together, but I can get it apart.