The efficiency and effectiveness of the rust removal of self-rotary ultra-high-pressure (UHP) derusting sprayers (UHP-DSs) heavily rely on the spatial arrangement and technical specifications of UHP water-jet nozzles. However, the current design approaches for UHP-DSs primarily depend on engineering guidance or experiential knowledge and lack precise theoretical analysis and optimisation frameworks. To address this gap, a novel integrated optimisation design method for UHP-DSs was proposed, which merges the CFD scheme with a spatial layout strategy for the nozzle to bolster system efficiency. First, a thorough hydrodynamic performance analysis of the UHP nozzle was conducted using the CFD method to identify the optimal process parameters. Following this, an accumulative impinging-duration optimisation model was developed to systematically evaluate the trajectory characteristics of UHP-DSs and ensure uniformity of the water-jet energy distribution. Second, a theoretical calculation model on self-rotary UHP-DSs was established to explain the correlation between the spatial arrangement of the nozzle and self-rotary speed. Finally, the optimal spatial arrangement of the nozzle was determined using the particle swarm optimisation algorithm to maximise water-jet energy uniformity, with the corresponding attack angles obtained via the theoretical self-rotary model. Experimental verification indicated that the proposed optimisation design method could effectively enhance the rust removal efficiency of UHP-DSs by approximately 44.1% compared to that of the original design scheme. Therefore, it has promising applications for improving ship maintenance practices in the maritime industry. •Propose an accumulative impinging-duration model to evaluate water jet energy distribution.•Propose a self-rotary model for rust-removing sprayer to achieve desired rotation speed.•CFD-integrated layout can boost rust-removing efficiency by 44.1%.