Comparing with head wave, coda wave propagates through a long path with multiple scattering and consequently can magnify reservoir velocity perturbations. Thus it is possible to detect slight wave velocity change caused by reservoir physical parameter variations with coda wave interferometry technique. In order to prove that coda wave can be used to detect reservoir velocity perturbations, rock physics experiment is performed firstly. Then, based on the wave equation stagger-grid finite difference method, numerical simulations for models with unperturbed and perturbed reservoir velocities are carried out, and coda wave interferometry is used to detect the corresponding slight wave velocity changes. Furthermore, the least velocity perturbation, which can be detected by coda wave interferometry, is also confirmed with numerical examples. Finally, we conclude that coda wave interferometry is efficient in detecting slight velocity change with a quantitative criterion.