Fault reactivation is an unfavorable incident during petroleum well drilling and production because the reactivated fault imperils the well integrity potentially. Coring and rock mechanics experiments are performed to obtain the rock properties of the fault in a Uganda oilfield. The three-dimensional finite element model of directional wells passing through reactivated faults is established. The mechanical behaviors of wells under various scenarios are analyzed by numerical simulation. The influence rules of slip displacement of fault, well inclination angle, wall thickness of casing, steel grade of casing and property of cement sheath on mechanical state of wells through faults are revealed. Research results indicate that decreasing the intersection angle between directional well and fault plane and employing cement sheath with low elastic modulus can enhance well integrity effectively. The research achievements provide the integrity assessment method and mitigation measures for the directional wells through reactivated faults.