Abstract: Abstract：Visualizing the fluid object in question can directly observe the fluid flow status. According to the relative theory in fluid dynamics, this paper analyzes the following characteristic of solid tracer element which is used to display air current. With the white powder of MgCO3 as tracer element which is directly put into the air stream, the result of the experiment are compared with that of the theoretical analysis. The results show that it is an effective way to display the air current with powder of MgCO3 as tracer element directly put into the air stream, which has characteristic of good visualization and easy track.