After a brief overview of the high energy heavy ion collisions and lattice QCD simulations at finite temperature and density, we report our lattice study of transport coefficients of quark--gluon plasma (QGP) in the lattice quench approximation. We discuss why the transport coefficients are important and interesting in QGP physics.

PACS numbers: 25.75.Nq, 12.38.Gc, 12.38.Mh, 24.85.+p