High-moisture extrusion is a hot frontier technology for developing novel plant-based meat analogues with meat-like texture. In this study, a soy protein isolate (SPI)-Nemipterus virgatus surimi blend at a ratio of 80:20 (m/m) was used to investigate the effect of hydrothermal parameter combinations (moisture content 65%, 70% and 75%; extrusion temperature 125, 135 and 145 ℃ ) on the specific mechanical energy (SME) and die pressure during the high-moisture extrusion process and the quality of extrudates. Results showed that under the conditions used in this study, the surimi gel was filled as particles in the SPI-surimi mixed gel structure, which could affect the formation of the oriented gel structure. Simultaneously increasing extrusion temperature and moisture content decreased SME from 783.40 to 410.96 kJ/kg and die pressure from 7.79 to 1.60 MPa (P < 0.05). The quality of SPI-surimi mixed extrudates was affected markedly by hydrothermal parameter combinations and the effect of moisture content was more significant than that of extrusion temperature. At a moisture content of 70% and an extrusion temperature of 145 ℃ , the fiber-like structure of SPI-surimi mixed extrudates reached its maximum (2.36). Under the hydrothermal parameter combination, the SME and die pressure were nonlinearly correlated with the hardness, chewiness, gel strength, water-holding capacity and shear force of SPI-surimi mixed extrudates. This study provides a reference for the development of novel alternative protein products combining animal and plant proteins which can complement each other with their advantages.