In this article, first, a sufficient condition for a starlike mapping of order f(x) defined on the unit ball in a complex Banach space is given. Second, the sharp estimate of the third homogeneous expansion for f is established as well, where f(z) =(f1(z), f2(z), · · · , fn(z))′ is a starlike mapping of order or a normalized biholomorphic starlike mapping defined on the unit polydisk in Cn, and D2fk(0)(z2)/2! = zk(∑nl=1aklzl), k =1, 2, · · · , n, here, akl = 1/2!∂2fk(0)/∂zk∂zl,k, l = 1, 2, · · · , n. Our result states that the Bieberbach conjecture in several complex variables (the case of the third homogeneous expansion for starlike mappings of order and biholomorphic starlike mappings) is partly proved.