The response of crop photosystem activity to a certain level of [CO₂] elevation have been widely concerned. However, long-term effects of elevated [CO₂] over multi-generations of crops received little attention. Using open-top chambers, we set up two treatments of elevated [CO₂] from 2016 to 2019 in rice (Oryza sativa) growing seasons. One treatment was stepwise increase (SI) of +40 µmol mol-1 per season, the other was constant increase (CI) of +200 µmol mol-1. Rice seeds harvested in each [CO₂] environment was planted successively. Seeds from ambient [CO₂] were also planted in SI and CI OTCs in next year to study the short-term effect. We measured the diurnal change in PSII functionality of leaf in 2019. Results showed that both SI and CI promoted PSII function. SI was more beneficial to improve efficiency of electron trapping and transporting in PSII and performance index of leaf. The maximal photochemical efficiency of PSII decreased linearly with increasing photosynthetic photon flux density throughout the day. Predawn efficiency decreased dramatically with the development of growth stages. Together, we found PSII efficiency benefit from multi-year [CO₂] elevation, which could help to better understand the response of electron transport to elevated [CO₂].