Abstract: In district 6-7 of the Tahe Oil Field, oil sands in high-yielding wells mainly locate at the top of Carboniferous Karashayi Formation. The sandbodies have small scale and thin thickness. When seismic resolution fails to identify thin sandbody, we can use the formation thickness changes of Karashayi Formation to predict the location of sandbody pinch-out boundary. Favorable lithologic traps may generate at where formation thickness changes obviously. We use wavelet decomposition to remove T⁵₀ strong reflection. The strong reflection of big formation is removed, and the weak reflection of thin sandbody is strengthened, which may help to identify the plane distribution range of thin sandbody.