Can it work? If so, what is the best way(mount) to do it? Thanks.
It works great with Aimpoints and EOTechs, but I suspect that what you mean is in the context of magnified day optics. My opinion is that it only works so-so, depending on the application.
I have experimented a bit with one of my bolt guns, and abandoned the concept without firing a shot. There are a couple of issues:
The first is making space for the monocular, about 5" worth. This generally means moving the day optic forward, which will likely cause some POI shift from the day position.
The second is light transmission. Even using a high quality optic with a very large objective, clarity above about 4-5x starts deteriorating pretty badly even in decent light. If you look at dedicated NV weapon sights or screw-on magnifiers, they have relatively low magnification and huge objectives; there is a reason for this.
To direct mount a monocular to a magnified day optic, one can use an uni-adapter or a monoloc. The former is substantially more economical, while the latter is arguably a bit more sturdy.
To mount a monocular on a rail behind a magnified day optic, most of the typical mounts should work just fine, although a PRI might be beneficial due to its adjustable height.
If your application is a .22LR, or an AR-type weapon with a very long continuous rail, you can probably get OK performance. If your application is a centerfire bolt gun, it may not work out quite so well. In any case, don't plan on cranking the magnification up very high.
Although I prefer Aimpoints, arguably the best setup is a Gen3 monocular with a mil-spec screw-on magnifier behind an EOTech. The magnifier and EO are actually less expensive than any magnified day optic that would work even reasonably well.
So far, I have had no bad experiences with such a set up. I use the MUM gen3 with a universal adapter setup on my 22mag bolt gun (primarily), AR carbine, 10/22 (lots and lots of fun w/ a silencer), and have also used it on several of my buddies' guns. With my AR I have been able to CONSISTENTLY hit milk jug sized targets out to 200+ yards. I'm fairly certain that I could go further, just have not tried. The range limitation, for me, came from the IR illuminator I am currently using. God forbid you are someone so lucky to have some sort of laser illuminator I have a feeling your range would be limited by the caliber of the rifle only. I have used it in passive mode (no illuminator) but it is not as impressive unless the moon is out. In starlight, it still works well w/o illuminator (on my glass at least), but having an illuminator on makes a HUGE difference. Yes, eye relief can be an issue if you let it be. Most of my stuff is not uncomfortable enough to warrant doing anything, but if it is, throw an extra butt pad onboard... problem solved. On a nice day scope, these things really kick ass, but mine even performs well on my bushnell cheapy and simmons super-cheapy. Would not use it behind an illuminated reticle day sight unless said sight has been designed with NV in mind (ex. eothingy, aimpoint, some version of the shortdot i think too). For me this setup makes a whole lot more sense than a dedicated riflescope, which i had tried and realized that i barely shot the gun anymore since it was only for night time. I love the hell out of my setup. Works well to have a spotter NV to use apart from the weapon mounted one, but is not absolutely necessary. I'll stop ranting...