Abstract: Pre-assessment can conduct the quantitative evaluation for influencing factors of fracturing effect and their relations, which could make the fracturing operation more scientific and quantification, and improve the operation efficiency for the target layer. At present, the pre-evaluation technique is aimed at whether the target wells or target layers are reasonable; for those re-operation wells or failed-treated wells, few or no analysis is engaged by such technology. The failure reasons of two fracturing operations for Layer Chang8 in exploration Well H136 in Changqing Area were analyzed, and some pre-evaluations including reservoir production capability, fracturing failure, fracturing liquids damage and re-evaluation of the shale content were performed, from which advantages and disadvantages for the third operation were obtained. Based on those a pad-acid variable rate stimulation method was carried out which have achieved the expected result. The successful practice of the third fracturing will provide technical references of effective development for further evaluated wells and key exploration wells in Ordos basin.