A newly developed μSR method combined with a tunable, high power and sharply pulsed laser was applied to GaAs. Anomalous transport phenomena of the photo excited effects into bulk crystal were observed, given that the stopping range of implanted muons is about 200 times larger than photo-absorption depth. In addition, the measurement of photon energy dependence of muon spin depolarization under laser irradiation suggests the impurity level associated with MuBC0 is located within the band gap of GaAs.