  We study the hadronic production of four-quark states with double heavy
quarks and double light antiquarks at LHC. The production mechanism is that a
color anti-triplet diquark cluster consisting of double heavy quarks is formed
first from the produced double heavy quark-antiquark pairs via $gg$ fusion hard
process, followed by the fragmentation of the diquark cluster into a four-quark
(tetraquark) state. Predictions for the production cross sections and their
differential distributions are presented. Our results show that it is quite
promising to discover these tetraquark states in LHC experiments both for large
number events and for their unique signatures in detectors.
