Summary Merits in the inherent safety characteristics and multiple applications, cause the pebble‐bed‐type nuclear reactors, including the High‐Temperature Gas‐cooled Reactors, Fluoride‐salt‐cooled High‐temperature Reactors and Water‐cooled Pebble‐bed Reactors, to gain more focus in recent years. Thermal‐hydraulic characteristics in the pebble bed reactor core are of great significance to the safety evaluation and design of such reactors. Experimental investigations on the thermal‐hydraulics of different fluids in the pebble‐bed‐type of nuclear reactor core have been reviewed in this paper. Main experimental methods to determine the flow regime transition, convective heat transfer coefficients, and effective thermal conductivity have been summarized, with the merits and disadvantages discussed. Discussions are given on the main factors that can influence the flow, convective heat transfer and effective thermal conductivity in the pebble bed.