This study investigates the mechanism by which low blue light (LBL) induces leaf senescence in soybean. The research reveals that GmCRY1s, rather than GmCRY2s, primarily regulate leaf senescence in response to blue light signals. Under normal light conditions, GmCRY1s interact with DELLA proteins, stabilizing them and suppressing the transcription of *GmWRKY100* to delay senescence. However, LBL disrupts this interaction, leading to the degradation of DELLA proteins and the upregulation of *GmWRKY100*, thus promoting leaf senescence. The study also demonstrates that *GmWRKY100* knockout soybeans show delayed leaf senescence and improved yield under natural field conditions, suggesting potential applications in enhancing soybean production by manipulating the leaf senescence trait. The findings provide insights into how plants perceive and respond to LBL signals to regulate leaf senescence.This study investigates the mechanism by which low blue light (LBL) induces leaf senescence in soybean. The research reveals that GmCRY1s, rather than GmCRY2s, primarily regulate leaf senescence in response to blue light signals. Under normal light conditions, GmCRY1s interact with DELLA proteins, stabilizing them and suppressing the transcription of *GmWRKY100* to delay senescence. However, LBL disrupts this interaction, leading to the degradation of DELLA proteins and the upregulation of *GmWRKY100*, thus promoting leaf senescence. The study also demonstrates that *GmWRKY100* knockout soybeans show delayed leaf senescence and improved yield under natural field conditions, suggesting potential applications in enhancing soybean production by manipulating the leaf senescence trait. The findings provide insights into how plants perceive and respond to LBL signals to regulate leaf senescence.