Some would recommend doing more exercise, but somehow after couple weeks of exercise(burn at least 150 calories everyday), the rate still stay the exactly the same. Is the rate working like a fixed number to body or do my body have problem with burning calories? If it is the case, is there any suppliments would help?
It is extremely difficult to measure TDEE (Total Daily Energy Expenditure) - the calories one's body uses in a day - because of how complex the body works, how many factors effect it, and how different each person is. 150 calories/day is a relatively small amount in the grand scheme, and probably will not affect you a ton, especially in the short term.
One surefire way to increase TDEE is to gain muscle, as each muscle cell uses much more energy, even at rest, than each fat cell. When you exercise, try shifting your focus from burning calories to building muscle (and you will still obviously burn calories in the process). You can do this by weight training and resistance training most simply - start out small, find techniques that work for you, and keep upping the intensity over time.