We study the regularity of weak solutions to a class of second order parabolic system under only the assumption of continuous coefficients.We prove that the weak solution u to such system is locally H(o)lder continuous with any exponent α ∈ (0,1) outside a singular set with zero parabolic measure.In particular,we prove that the regularity point in QT is an open set with full measure,and we obtain a general criterion for the weak solution to be regular in the neighborhood of a given point.Finally,we deduce the fractional time and fractional space differentiability of Du,and at this stage,we obtain the Hausdorff dimension of a singular set of u.