The existing three-dimensional micro-particle image velocimetry systems obtain the spatial position of tracer particles through scanning or imaging from multiple perspectives, which leads to the complexity of the system and difficulty in making an instantaneous measurement of three-dimensional velocity in micro-scale flow. In this paper, a light field micro-particle image velocimetry technique based on a microlens array is proposed. In this technique, the instantaneous light field information of tracer particles in the micro-scale flow field can be recorded by a single camera in a single photographic exposure. Further, in combination with the point spread function model of the light field microscopic imaging system calculated by wave optics theory, the instantaneous spatial position distribution of tracer particles in the micro-scale flow field can be reconstructed by a deconvolution method. The reconstruction resolution and the spatial position error are analyzed and discussed. Experiments on micro-scale flow field reconstruction are carried out, and the feasibility of the reconstruction method for light field microscopic imaging is verified.