Abstract: The safety situation in the construction industry across the world has been complicated for a long time, and the high incidence of accidents poses great challenges to this situation. Research on occupational safety and health indicates that people are prone to misconduct or unsafe behavior when they are tired. A large number of accident analyses show that fatigue is one of the most important reasons for accidents. When the human body enters into a fatigue state, the physiological parameters change accordingly. The aim of this study was to investigate the effects of heart rate and heart rate variability (HRV) on physiological fatigue in a sustained bricklaying task. A mathematical model was proposed for evaluating physiological fatigue. Five male healthy participants were selected to imitate construction by engaging in bricklaying on an 86 cm platform. HRV data were collected every 30 min during the sustained task, and heart rate was measured every minute. Analysis of variance, one-sample t-test, and nonlinear curve fitting were adopted in this study. Physiological fatigue shows a significant change with heart rate fluctuation (significant level α=0.05, P<0.05). With an increase in physiological fatigue, the heart rate needs a longer time to decrease to the normal level. No significant difference is observed in HRV between the subjects (α=0.05, P>0.05). The trend of the physiological fatigue curve follows a cubic function. The nonlinear curve fitting results (R²=0.8892) show that the development trend of physiological fatigue shows an "S" trend, which can be divided into the following three stages:fatigue adjustment period, fatigue stability period, and fatigue instability period. Proper rest in the fatigue failure period (In this experiment, it was about 90 min.) can slow or delay physiological fatigue.