Abstract: In the tritium breeding regions of helium cooled solid blanket of fusion reactor, the pressure drop characteristics of helium in packed pebble beds are of great significance to the design of the pump power. Based on the background of the tritium breeding regions, the effects of helium flow rate, particle diameter, and the channel length on the pressure drop characteristics were investigated in packed pebble beds. The test section is a rectangular channel with the size of 20 mm×20 mm×500 mm. Flow rate is within 0.1-0.6 m/s and particle diameter is 0.5, 0.8, 1.0, 1.5, 2.0 mm in this experimental study. The experimental results show that pressure drop is positively correlated with the helium flow rate and channel length of beds, and pressure drop is negatively correlated with particle diameter. Compared with Ergun correlation, the experimental values are higher than the calculated values of Ergun correlation in condition with smaller particle diameters due to the effects of the compressibility. Ergun correlation modified with the compressibility was deduced by the momentum equation. The results show that the calculated values of Ergun correlation modified with the compressibility are in good agreement with the experimental data. This study would provide the data support for the design of the tritium breeding regions and the verification for the numerical simulation.