design: GA3 is widely used as a common chemical regulator in agricultural production. The degree of endocarp lignification in walnut affects its yield, disease resistance and seed kernel quality, however, its molecular mechanisms have been less studied. Our results indicate that 100 mg/L GA3 promotes endocarp lignification in the early stages of shell hardenings of 'Qiang Tele' walnut. Transcriptome sequencing analysis of walnut with GA3 treatment revealed that MYBs were primarily involved in GA3-induced regulation of endocarp lignification.