Wenchuan earthquake (M_S 8.0) occurred in the section of the Longmenshan fault where slow strain had accumulated. The authors calculate the stress accumulation in the lithosphere of the Longmenshan fault area, the co-seismic stress change and the post-seismic stress relaxation to estimate the Wenchuan earthquake recurrence interval. It is shown that the eastern movement of Tibetan Plateau resulting from the India-Asia collision is obstructed in the Longmenshan fault area by the strong Sichuan Basin. The recurrence interval of Wenchuan earthquake is estimated to be 5 400 years corresponding to the time needed to accumulate the magnitude of the stress drop of the earthquake based on visco-elasticity.