Abstract: It is significant for the development of multidimensional two-phase models to study the measurement technology and distribution characteristics of local parameters in two-phase flow. The radial distribution of a rising bubble in stagnant liquid is investigated through the radial measurement in a vertical tube using the dual-sensor optical probe. The analyses of probe signals show that optical probe is very sensitive to the bubble signals and satisfactory measurement results can be obtained. Besides, the effect of the up-stream sensor on the down-stream one is studied in this paper.