  We compute the production cross section of a pair of Standard Model Higgs
bosons at the LHC at next-to-leading order in QCD, including corrections in
inverse powers of the top quark mass. We calculate these power corrections
through ${\cal O}(1/M_t^8)$ and study their relevance for phenomenology of the
double Higgs production. We find that power corrections are significant, even
for moderate values of partonic center-of-mass energies, and that convergence
of the $1/M_t$ expansion can be dramatically improved by factorizing the
leading order cross section with full $M_t$-dependence.
