  We calculate the decay rate of light scalar mesons, using a diquark chiral
effective theory, recently proposed to describe exotic hadrons. In the
effective theory the light scalar mesons are postulated to be bound states of
diquark and anti-diquark. We find our results are in good agreement with
experimental data. The axial couplings of diquarks with pions and kaons are
found to be quite small and the perturbation is reliable. It shows that the
diquark picture captures the correct physics of light scalar mesons.
