A calculating method is proposed for lightning transient analysis in photovoltaic bracket systems. The circuit parameters are evaluated for the conducting branches and grounding electrodes. On the ground of the circuit parameters, the equivalent circuit model is set up for photovoltaic bracket systems. The transient calculation is made by the circuit model and the potential and current responses are obtained in photovoltaic bracket systems. The laboratory-experiment is performed on a reduced-scale photovoltaic bracket system. The results obtained from the measurement are compared with those from the transient calculation to confirm the validity of the circuit model. Then, the probability density function of lightning current is further introduced into the statistical analysis of lightning transients. By means of the transient calculations made in a large interval of lightning current amplitudes, the statistical values of the nodal potential and branch current amplitudes are calculated by probability weights. A numerical example is also given for examining the difference between the statistical and non-statistical values. The proposed method can take account of the actual randomness of lightning discharge and afford a sound basis for lightning protection design of photovoltaic bracket systems.