The effects of heat treatment on microstructure and hardness of laser surface-clad Ni21+20%WC+0.5%CeO2 on the heat-resistant cast iron were investigated by means of X-ray diffraction(XRD), transmission electron microscope(TEM)and microhardness test. The experimental results showed that heat-treating at 500℃ has no effect on microstructure and hardness of the layers. Although the phase composition of the layers heat-treated at 700℃ and 800℃ remain unchanged,more Ni3B and Ni4B3 phases are precipitated on the matrix of the cladding layer, the metastable phase-M7C3 is transformed into steady phase-M23C6, and the precipitated phases coarsened.