  We calculate the constant term of Coleman power series and use it to prove an
analogue of Iwasawa Main Conjecture in function fields of characteristic p>0
using Euler systems. This result is proved by a similar method of classical
proof of Iwasawa Main Conjecture, go back to Kolyvagin and Rubin. We construct
Euler systems from theta function of Drinfeld modules and establish
finite-singular comparison equation even when p is not invertible the
coefficients.
