High temperature strength of hydrogen annealed silicaon wafer was investiaged. Wafers were 150mm in diameter, Czochralski-grown(100) silicon crystal. Silicon wafers were annealed at $1200^{circ}C$ for 1 hour in a hydrogen atmosphere with a heating rate of $10^{circ}C/min$ and $20^{circ}C/min$ in an hot-wall furnace. Oxygen precipitate density in slow heating rate sample and rapid heating rate sample were $2{ imes}10^{9}/cm^3$ and $3{ imes}10^{7}/cm^3$, respectively. Decreasing the heating rate increases the oxygen precipitate density. The strength was measured by the three-point bending test at $1000^{circ}C$ using strip-shpaped samples cult from silicon wafer. The maximum resolved shear stress($T_{max}$) at the specimen surface converted from the maximum load was dependent on strain rate and oxygen precipitate density constained in the silicon wafer. The $T_{max}$, 20.5 MPa for as-received samples, was reduced to 17.9MPa in slow heating rate sample. On the other hand, the $T_{max}$ was almost the same as 20.3 MPa in rapid heating rate sample under a strain rate of $6.9{ imes}10^{-6}/s$ at $1000^{circ}C$.