The orientation modulation properties of 597 cells in cat dLGN were studied using drifting sinusoidal grating as stimulus, while the feedback project from cortex was blocked through cortical ablation (including area 17, 18, 19 and LS). The average orientation bias of neurons was 0.154 in dLGN of decortiate cats, similar to that of normal cats (0.155). The optimal orientation tended to horizontal in decortiate cats as that in normal cats. However, the cells lossed the tangent distribution of the optimal orientation in decortiate cats. Similar results were observed in cats whose visual cortex were silenced by GABA or KCl. The results suggested that the tangent distribution of the optimal orientation in normal dLGN was generated from the feedback projection from visual cortex.