Abstract: The staining method was used to study the shape and properties of flow field in a cup continuous precipitation reactor. And the distribution and diffusion of precipitated particles in the central eddy region were investigated in two ways, namely, the addition of particles and the formation of particles by instant precipitation reaction. At 26 ℃, the effects of feeding method, stirring speed and apparent reaction time on the particle size distribution and average particle size of the precipitated oxalate particles, surface particles attachment of reactor and stirred paddle were investigated in a cup type continuous precipitation reactor. When both oxalic acid and ferrous sulfate solution are added from the central eddy current region in a cup precipitator, the particle bonding and agglomeration can be avoided in the inner wall of the reactor, and the average size of the particles is relatively large, in which the proportion of the particle size of 2.5 μm and <10 μm was relatively small. When the stirring rate is in the range of 500-800 r/min, increasing the stirring speed is unfavorable to the formation of precipitates with particle sizes of 2.5 μm and <10 μm. When the apparent time of the continuous precipitation reaction of ferrous oxalate is longer than 30.0 minutes, the growth rate of the precipitated particles gradually slows down.