For a taxpayer to claim someone as a dependent, the purported dependent must have a US social security number (or an individual tax identification number).
Since you are in the US on a visa, that likely means that your parents do not have social security numbers and are not eligible for social security numbers.
Moreover, for you to claim a person as a dependent, certain requirement must be met. One requirement is that the person is a US citizen or US resident alien for some part of the year. For more information, check out Publication 501 available for free at www.irs.gov .