Aimed to investigate the effects of water regulation under straw return conditions on rice yield and soil fertility. A field experiment was conducted using the rice variety“Jijing 830”in a split-plot design. The main plots consisted of two straw management practices: no straw return (A₁) and full straw return (A₂). The subplots comprised five water regulation treatments: mild water control (WP₁, Ψsoil = 0 kPa), moderate water control (WP₂, Ψsoil = -15 kPa), moderate-severe water control (WP₃, Ψsoil = -30 kPa), severe water control (WP₄, Ψsoil = -45 kPa), and a conventional flooding treatment (CK) as the control. The results showed that the A₂-WP₃ yielded the highest, with a 22.5% increase compared to the A₂-CK at the late tillering stage. In contrast, at the jointing-booting stage, the A₁-WP₄ and A₂-WP₄ resulted in yield reductions of 32.2% and 19.8%, respectively, compared to their corresponding CK. The straw decomposition rate was higher when water regulation was applied at the late tillering stage than at the jointing-booting stage. Furthermore, appropriate water regulation effectively enhanced the supply capacity of soil nutrients. In comprehensive consideration of all factors, the integration of full straw return with moderate-severe water control (WP₃，Ψsoil = -30 kPa) at the late tillering stage can synergistically achieve increased rice yield, improved soil fertility, and enhanced straw decomposition efficiency.