Approximately 49% of China’s jujube production originates from Xinjiang. Appropriate irrigation and fertilization strategies are critical for improving jujube quality and yield. Current research has primarily focused on the effects of different irrigation regimes on jujube growth, while systematic studies investigating the relationship between potassium application rates and yield are still lacking, hindering the development of fertilization guidelines. This study investigated the effects of different potassium application rates (K; 240, 180, 120, and 0 kg·hm⁻²) on jujube yield and transpiration rate. The results demonstrated that potassium fertilization enhanced root water uptake and significantly promoted jujube growth and development. A water and potassium transport model in jujube root zone and jujube yield models were established using the experimental data of four potassium application treatments under the conditions of drip irrigation and potassium application. Additionally, 9 sets of orthogonal numerical experiments were designed with irrigation and potassium application rates as variables. The results showed that irrigation amount, potassium application rate, and their interaction all contributed to jujube yield variation, with the water–potassium interaction accounting for the largest contribution. The lateral extent of potassium movement in the jujube root zone under drip irrigation reached approximately 80–100 cm. Within the affected zone, potassium concentration declined significantly with increasing distance from the roots, while potassium outside the zone infiltrated vertically into deeper soil layers along with the irrigation water. The economic benefits of jujube were maximized at irrigation amounts of 240–320 mm and potassium application rates of 240–360 kg·hm⁻². This study established empirical equations relating jujube yield, transpiration rate, and net income to irrigation and potassium application rates under drip irrigation, providing guidance for irrigation and potassium management of drip irrigated jujube in arid regions.