This paper presents a neutronics design of a 10 MW ordered-pebble-bed fluoride-salt-cooled high-tem-perature experimental reactor. Through delicate layout, a core with ordered arranged pebble bed can be formed, which can keep core stability and meet the space require-ments for thermal hydraulics and neutronics measurements. Overall,objectives of the core include inherent safety and sufficient excess reactivity providing 120 effective full power days for experiments.Considering the requirements above,the reactive control system is designed to consist of 16 control rods distributed in the graphite reflector. Com-bining the large control rods worth about 18000-20000 pcm,molten salt drain supplementary means (-6980 to -3651 pcm) and negative temperature coef-ficient (-6.32 to -3.80 pcm/K) feedback of the whole core,the reactor can realize sufficient shutdown margin and safety under steady state. Besides, some main physical properties,such as reactivity control,neutron spectrum and flux,power density distribution,and reactivity coefficient, have been calculated and analyzed in this study. In addi-tion,some special problems in molten salt coolant are also considered,including 6Li depletion and tritium production.