Hydrogen fuel will be a potential energy source for internal combustion engines in the future. A promising approach for improving the efficiency and achieving zero-emission is to employ the noble gas argon. The work of this paper aimed at investigating the cyclic variation of argon power cycle engine with fuel of hydrogen. The engine has been modified based on a 0.4 L, one signal cylinder diesel engine into spark ignition engine with a port fuel injection system. The influencing factors on the cyclic variation in the argon power cycle engine with fuel of hydrogen, such as type of working gas, ignition timing, compression ratio (5.6, 6.9, and 7.35), and CO2 fraction in the mixture of argon and oxygen, were test in this study. The results show that compared to air, higher indicated mean effective pressure (IMEP) and better engine operation stability could be achieved under an atmosphere of argon and oxygen. And coefficient of variation (CoV) in both maximum pressure (Pmax) and IMEP could be reduced. Because of the knock limit, the ignition timing of argon power cycle engine with fuel of hydrogen was set in around TDC which range from 11°CA BTDC to 5° ATDC. There is an optimum ignition timing to make the smallest CoVIMEP and CoVPmax for each operating condition. The correlation coefficient R (Pmax, IMEP) is not very sensitive to the ignition timing. There is a strong relevance between CA10 and CA50, combustion cyclic variation is mainly caused by flame development period. With the increase of compression ratio, more stable hydrogen combustion, smaller CoVIMEP and CoVPmax could be achieved. With the increase of CO2 fraction in the mixture of argon and oxygen, the heat release rate becomes slower, engine operation stability worsens, and causes CoVIMEP increasing.