Abstract: This paper studied the Vondrak filter and its criteria of functions.The thesis analyzed existing evaluation for the vondrak's filter.The existing criteria for evaluation of Vondrak filter was cross correlation coefficient and root-mean-square error(RMSE),which had some weak point in some place.A new criteria for evaluation was proposed that square root(δ) of the linear combination,which was the squre of root-mean-square error and the smoothness.The new criteria for evaluation was a quantitative index.The practicability and the advantage of the new criteria for evaluation has been demonstrated through simulated data.