Abstract: The reservoir sensitivity evaluation is to studythe reservoir harm mechanism, provides the reliable basis forthe reservoir protection. The Ordos basin Zhang Han areareservoir nature is bad, belongs to the midhole-low permeability to the low hole-extra low permeability reservoir. We started from the sensitive experiment analysis,measure different sample sensitive index, thus analyzed anddetermined its various sensitive characteristic. The resultsindicated finally this local sensitive characteristic besides alkali sensitively for weakly to medium weak, other "four sensitive" do not have or have weak sensitive characteristic,therefore, in exploration and development process main consideration is reservoir alkali sensitivity. In addition, throughthe research of different speed of flow-penetration coefficient relations curve, the velocity sensitivity formation mechanism has verified.