Abstract: The output characteristics of solar cells are not only related to load,but also affected by the external environment. It is necessary to adopt the maximum power point tracking technology to improve the photoelectric conversion efficiency. Combined with the foraging characteristics of bacterial population,a maximum power point tracking strategy with good dynamic response under a fluctuant illumination condition is proposed in this paper. The calculation models of swimming step size and migration probability with the change of bacterial fitness value are presented by optimizing the chemotaxis operation and migration operation of traditional bacterial foraging algorithms. The fitness function of bacteria and the initial position of individual bacteria are determined based on the output characteristics of solar cell and maximum power point tracking mechanism. The simulation results show that compared with the traditional bacterial foraging algorithm,the response time and the output power error are reduced to 0.18 s and 0.8%,respectively when the PV array is blocked by static shadow,and response time is only 0.2 s when the PV array is covered by dynamic shadow using the proposed method.