In this paper, a holographic off-axis 4F optic system is used to record 3D hologram of spray field. The advantage of recording spray field using this system is described. And image processing of this particle field hologram is achieved. We also describe several algorithms--the morphology algorithm which is fit for automatic analysis of particle hologram, partial meaning and camber fit threshold method, a method of particle pairs judgment based on coherence value, a method of plotting the over-lay particle pairs based on the edge shapes. In the end, the processing result of a double-exposed particle field hologram is given out including statistical figures of the size, quantity and velocity of particles.