  In this paper, we show that if the mean curvature of a closed smooth embedded
mean curvature flow in R^3 is of type-I, then the rescaled flow at the first
finite singular time converges smoothly to a self-shrinker flow with
multiplicity one. This result confirms Ilmanen's multiplicity-one conjecture
under the assumption that the mean curvature is of type-I. As a corollary, we
show that the mean curvature at the first singular time of a closed smooth
embedded mean curvature flow in R^3 is at least of type-I.
