I work10-16 hrs front of monitor. Till I have no problem. Sometime it automatically drop water 4m eyes. What should I have to do protecting my eyes?

Blink more often. Long term close work of any kind leads to diminished blinking subconciously. This can lead to eye dryness and irritation. I have found it useful for my patients to look away every 15 minutes and blink several times. This usually is sufficient to restore comfort and easy focusing. If this does not work then you need to be evaluated for underlying silent potential disease.
How to prevent. Vision loss should be one of your concerns. Please try to break up that 10 to 16 hr stretch. You need to spend a few minutes away from the monitor looking at something far away, preferably nature or something natural like an indoor plant. The radiation from computer monitors over 3 to 4 hours can be damaging to the eyes. You are still young, but you need to prevent future eye damage.