Abstract: Based on the research of tight arrangement reactor, experiment investigation on Critical Heat Flux（CHF） for tight arrangement spiral-fin fuel assembly was performed. Results show that the CHF happens on the hot rod of fuel assembly, and when the CHF happens, the temperature of the heated wall will increase quickly, and the pressure will increase and the massflow rate will decrease at the same time. The pressure of the system, the mass flow rate, the quality and degree of subcooling have vital effects on CHF; The CHF relation of the tight arrangement spiral-fin fuel assembly was obtained based on the test data. The deviation between the proposed correlation and experimental data is less than 10%.