Molecular dynamics simulations of hydrogen isotope-covered silicon(111) and (110) surfaces based on the Bloch-Redfield theory were carried out to calculate the lifetimes of hydrogen isotope stretching modes on these two silicon surfaces at high temperatures. The computations gave lifetimes of 1700 and 500 ps for the Si-H stretches on H/Si(111) surface at 300 and 460 K, in good agreement with the experimental results of 950 and 550 ps, respectively. The calculations for the isotope Si-D,T stretches gave lifetimes on the time-scale of tens of picosecond at room temperature. Thermal effect and the precision of calculated lifetimes are discussed.