Barley, rich in beneficial ingredients, has been recognised as a healthy food and is widely used in the production of healthy foods for humans. The current study identified a new barley mutant with the SSIIa, SSIIIa, SBEIIa, and SBEIIb genes inactivated in the genome-edited offspring of targeted mutagenesis of starch synthetic genes using multiplex genome editing. The grain compositions and starch properties of the ssIIa/ssIIIa/sbeIIa/sbeIIb mutant were analysed and compared with the corresponding parameters of ssIIa, ssIIIa, sbeIIa/sbeIIb, ssIIa/sbeIIa/sbeIIb, and non-genome-edited lines (NE), respectively. ssIIa/ssIIIa/sbeIIa/sbeIIb exhibited the highest contents of β-glucan and amylose content among all mutants and NE, but not the most prominent in resistant starch, fructan, and fibre contents. The loss of SSIIa, SSIIIa, SBEIIa, and SBEIIb genes also resulted in significant changes in starch properties. This study enriched the genotypes of healthy barley and provided a theoretical basis for improving barley quality.