  We propose in this work an effective field theory description of the chiral
spin liquid state in Heisenberg spin system on kagom\'e lattice.To this end, we
derive the low-energy effective theory of kagom\'e (isotropic) Heisenberg
antiferromagnet around its ordered ground states found numerically and show
that quantum fluctuations induced by further neighbor spin exchanges are
equally strong as those from first neighbor.We use a chiral order parameter
theory to argue for the occurrence of finite temperature chiral symmetry
breaking transition into chiral ordered state in kagom\'e antiferromagnet with
further neighbor spin exchange interactions.We compute the chiral symmetry
breaking term in the effective ground state energy and show that chiral spin
liquid necessarily occurs in the ground state of kagom\'e antiferromagnet with
the first three nearest-neighbor spin exchange interactions.Finally, we
consider the quantum criticality of the kagom\'e antiferromagnet and show that
a Chern-Simons term emerges naturally at the transition between two ordered
states that satisfy appropriate `matching condition' that we derive, providing
explanation for why chiral spin liquid could occur at the transition between
appropriate ordered states.This emergent Chern-Simons term is the low energy
effective theory of the chiral spin liquid state, where the chirality is the
immediate consequence of the breaking of discrete symmetries by this
topological field theory.
