As a method of coherence algorithm based on eigenstructure,the core of C3 algorithmitsis suppressing continuity and emphasizing discontinuity of underground media by computing the coherence of time slices,and finally obtains both higher lateral resolution and lower dip resolution.To improve dip resolution,an improved C3 method,with computing covariance matrix by survey line instead of dealing with sliding panels is presented.The results show the new method has better resolution both in horizon and dip direction.