Abstract: In pebble-bed high temperature gas-cooled reactor, the detection and number counting of the spent fuel pebbles discharged from the reactor core are the crucial part for fuel monitoring. To meet the requirement by IAEA for nuclear security of pebble-bed high temperature gas-cooled reactor, a new detection scheme based on a principle independent of the existent eddy current detection should be developed for fuel distinguishing and counting in the fuel handling system’s pipeline. Based on γ measurement, a novel detection scheme was proposed, a prototype of the detector was designed, and its function was examined when the reactor was in steady-state operation. With the radionuclides’ data from the reactor HTR-10, through Monte Carlo simulation and analysis for the process when pebbles of various velocities and burnups passing through the detecting area, the reliability of the scheme for the distinguishing and counting for single fuel pebble was verified. Meanwhile, the feasibility of this scheme to detect the pebble flow was preliminarily proved. The result provides the designing foundation for scheme’s improvement and device production in the future.