Two tests of refilling and reflooding in the horizontal geometry channel under different pressure conditions, respectively, are conducted to understand the thermal hydraulics behavior during a LOCA in the CANDU reactor. One case of refilling a hot horizontal tube test and four cases of reflooding a horizontal fuel channel test series (35% and 60% break size of reactor inlet header with single-end injection or both-end injection, respectively) have been simulated. The horizontal channel is simulated with the model splitting as parallel pipes with cross flow junction component. The simulation results have been compared with the tests in terms of wall temperature or heated-pin surface temperature. The results are reasonably acceptable and it shows that the code is applicable on horizontal channel quenching.