Abstract: As circulating fluidized bed (CFB) boiler parameters increase, the number and size of cyclone separators continually evolve. With multiple separators arranged in parallel, gas-solid flow at the separator inlets becomes prone to non-uniformity, affecting furnace combustion and safety. A full-circuit geometry model is developed for a 660 MW supercritical CFB boiler. Using the continuum particle fluid dynamics (CPFD) method, numerical simulations investigated how separator inlet structures influence material distribution across six "H"-arranged separators. Results reveal that the intermediate separator's inlet position, furnace screen superheater arrangement, inlet angle and height, and hearth protrusion height all impact material distribution. An "eccentric-axisymmetric" front-wall inlet position for the intermediate separator, combined with uniform furnace screen arrangement, minimizes particle flow deviation. Reducing the intermediate separator's inlet angle initially decreases then increases deviation, reaching a minimum at 65.6°. Increasing the intermediate separator's inlet height similarly first reduces then raises deviation, with optimal uniformity at 9.25 m. Above 9.5 m height, the intermediate separator exhibits smaller inlet deviation but greater particle flow than side separators. For the furnace roof bulge, deviation follows the same trend, achieving minimal imbalance at 300 mm height.