Four months after the Wenchuan Ms 8 earthquake in west Sichuan (China), in situ stress measurements were carried out along the Longmengshan fault zone, with the purpose of obtaining stress parameters for earthquake hazards assessments. In situ stresses were measured in three boreholes by using overcoring of the piezomagnetic stress gauges for shallow depth and hydraulic fracturing for deeper depth. The results show that the maximum horizontal stress at shallower depth (~20m) is about 4.3 MPa, oriented N19°E, in the epicenter area at Yingxiu Township, and about 9.7 MPa, oriented N51°W, at Baoxing County in SW Longmenshan, and about 2.6MPa, oriented N39°E, near Kangding, at the southernmost area of the Longmenshan fault zone. Hydraulic fracturing was conducted at depths from 100 to 400 m and the results show tendency towards increasing in stress with depth. Compared with the results measured before the Wenchuan earthquake along the Longmenshan fault zone and in the Tibetan Plateau, it is concluded that stress level remains relatively high in the southwestern segment of the Longmenshan fault zone, and is still medium in the epicenter zone. These results provide key appraisal for future assessments of earthquake hazards of the Longmenshan fault zone and aftershock occurrences.