In FSX, if side wind is blown in cruise, planes crab to go right direction. But humans feel bad if the heading is different from the track.So in reality how do they do? Just crabbing or wing-low by autopilot systems?

A 'slip' would be very inneficient.. so even an autopilot just flies the heading needed to stay on course.At cruise altitudes, pax hardly notice, if at all..

In real life, take a look skyward on a windy, clear day with contrails visible. You may notice that the airplane and its contrail are collectively sliding across the sky in the direction of the high-altitude winds. The plane and contrail look absolutely straight and true, but the high altitude winds are sliding all of that along in a different direction. If you extrapolated this motion relative to you on the ground, yes - the plane is actually crabbing a bit! But, when you're in the airplane itself, it becomes really difficult to detect the difference in motion that the wind is providing unless the winds aloft are abnormally strong.For all intents and purposes, the airplane is traveling "straight and level" with respect to the wind... but the wind, like a river, is moving everything in its direction, so the airplane sets up on a course which takes this flow into effect, introducing a "crab" which would be seen if you examined the airplanes direction of travel and direction of the nose relative to the ground. In MSFS, there seems to have been a problem making the contrail act as an item in the wind like the airplane is... if I remember correctly, the contrail ends up coming off the plane at an angle equal to the crab, making things look a lot more "interesting" in the simulator than what they are in real life. Things seem a little exaggerated in the simulator with respect to this. A crab is noticible when you compare your direction of motion against something still, like the ground. At high altitude, you don't get a good opportunity to make this comparison because your field of vision is so huge. Closer to the ground, any crabbing would become more and more apparent to a passenger, because you're frame of reference against the ground gets better and better. BUT, up high, it's probably unlikely you'd see or notice it as a passenger. Now that 2 year old sitting behind you crabbing... THAT you might notice at cruise.-Greg

But humans feel bad if the heading is different from the track.

I see absolutely no reason why this statement shoule be true, especially in cruise, like the gentleman above me pointed out. :( Never ever have I seen or heard anyone who had even noticed an airliner was crabbing, let alone feeling bad because of it. Furthermore you can only look out sideways, so you can't even judge what direction either heading or track are from a pax POV IMHO. Moreover, don't forget your usual TAS on an average flight will be in the four-hundreds, now go ahead and calculate some WCAs for some average winds and you should see crabbing will usually be required in single-digit degree ranges only. Should not be a concern to anyone. Flying low-wing all the time though would probably set quite a few more folks nervous after a while. I know you could eventually get sick in a small prop in IMC when flying as a pax, but I doubt this happens as easily in airliner. :(