The heat treatment machine based on immersion was developed to reduce temperature difference during netting process and appraised it performance compared current heat treatment machine using high pressure. It was also reviewed the optimum heat treatment procedures for PBSAT monofilament net in accordance with the immersion time and temperature. The procedure was based on physical measurement such as breaking load, elongation and angle of the mesh for PBSAT monofilament. The water temperature gap of the treatment machine based on immersion was less than 1°C. and the energy consumption was also increased in high temperature condition. It was identified that the optimum temperature was 75°C and its optimum processing time was between 15 minutes and 20 minutes to get qualified physical properties.