An organic anti-reflective polymer which prevents back reflection of lower film layers and eliminates standing wave that is occurred by a thickness change of photoresist and light, in a process for fabricating ultrafine patterns that use photoresist for lithography by using 193 nm ArF and its preparation method. More particularly, the organic anti-reflective polymer of the present invention is useful for fabricating ultrafine patterns of 64M, 256M, 1G, and 4G DRAM semiconductor devices. A composition containing such organic anti-reflective polymer, an anti-reflective coating layer made therefrom and a preparation method thereof.