The invention relates to a focus detecting and controlling device of an aerial camera. The device is provided with three transmitting party grids and three receiving party grids which are respectively arranged above an image surface, on the image surface and below the image surface; rays emitted by a constant light source illuminate one side of each transmitting party grid by a scattering mirror and are reflected to the vicinity of a corresponding receiving party grid by a camera optical system, light energy transmitting the three receiving party grids is respectively received by three photovoltaic devices, and a focusing controller collects the peak voltage values of the three photovoltaic devices, judges the optimal focusing plane position and drives a focusing reflector to move to the optimal focusing plane position for a camera to image. Because each of the transmitting party grids and each of the receiving party grids respectively comprise the three grids which are respectively arranged above the image surface, on the image surface and below the image surface, the distance difference of the three grids in an optical path is the focal depth of a one-time camera optical system so that the information of collected peak voltage values is surely different at the same time to benefit the judgment of the focusing plane position, save the focus-detecting time and improve the focus-detecting precision.