We have developed a method to measure carrier recombination lifetime in crystalline silicon with the photo-muSR technique. The key of the method is to measure the dependence of relaxation rate of muon asymmetry on the excess carrier density, and characterise it by a power law. The method is also applicable in higher injection levels by increasing the applied longitudinal field. We found that the power is the same (0.7) in the lower three injection conditions, but changes to 0.4 in the highest one, indicating that the high injection level (or the high field) induces a change in the interaction between muonium centres and excess carriers. This proposal investigates the change in the power in detail, and study the muonium interaction and associated dynamics.