  Due to the potential applications in the low-power-consumption spintronic
devices, the quantum anomalous Hall effect (QAHE) has attracted tremendous
attention in past decades. However, up to now, QAHE was only observed
experimentally in topological insulators with Chern numbers C= 1 and 2 at very
low temperatures. Here, we propose three novel two-dimensional stable kagome
ferromagnets Co3Pb3S2, Co3Pb3Se2and Co3Sn3Se2that can realize QAHE with high
Chern number of |C|=3. Monolayers Co3Pb3S2, Co3Pb3Se2 and Co3Sn3Se2 possess the
large band gap of 70, 77 and 63 meV with Curie temperature TC of 51, 42 and 46
K, respectively. By constructing a heterostructure Co3Sn3Se2/MoS2, its TC is
enhanced to 60 K and the band gap keeps about 60 meV due to the tensile strain
of 2% at the interface. For the bilayer compound Co6Sn5Se4, it becomes a
half-metal, with a relatively flat plateau in its anomalous Hall conductivity
corresponding to |C| = 3 near the Fermi level. Our results provide new
topological nontrivial systems of kagome ferromagnetic monolayers and
heterostructrues possessing QAHE with high Chern number |C| = 3 and large band
gaps.
