Abrasive water jet technology has been applied to strengthen the surfaces of complex shapes and high-strength components to improve their fatigue life. In this regard, the energy distribution affects the strengthening; hence, its uniformity must be comprehensively investigated. The main parameters affecting the energy-distribution uniformity are the particle performance parameters, particle velocity distribution, particle spatial distribution, and overlap. In this study, theoretical models of single-pass energy distribution and multipass lap energy distribution are established by considering the spatial and velocity distributions of particles. Additionally, the ratio of the energy difference to the maximum energy in the lap range is determined as the index of energy-distribution uniformity. Based on the relationship between deformation and energy, the theoretical model is verified using 18CrNiMo7-6 alloy steel. Results show that the maximum theoretical deformation in a single pass is consistent with the experimental results, with an error of less than 6%; additionally, the theoretical and experimental peak and trough differences after a multipass lap show good agreement. Using the proposed model, the lap distance can be obtained to guide practical engineering applications.