We have extended the Cooray-Rubinstein formula into a roughand ocean-land mixed propagation path. Note that, in such a case, the horizontal electric field over the land section is related to the conductivity and roughness. When the field propagates from the rough ocean surface to the land section, it shows that the decrease of rough-land conductivity results in a more negative excursion magnitude of the horizontal field waveform. However, the increase of the land-section roughness causes the decrease of the horizontal electric field. When the land conductivity is larger than 0.01 S/m, the horizontal field is more affected by the land roughness. When the land conductivity is less than 0.001 S/m, the effect of the rough-land section within the root-mean-square height of 1 m can be ignored.