The objective of the present study was to develop predictive models for the growth of Staphylococcus aureus on fresh-cut spinach influenced by temperature (15, 25, and $35^{circ}C$) and relative humidity (60, 70, and 80%) using newly developed OH-Fit V1.0 software. The experimental data at each combined condition were collected and indicated that temperature played a more important role than relative humidity on growth behavior of S. aureus. Firstly, primary and secondary models were developed in sequence using the modified Gompertz and polynomial equation, respectively. After external validation using independent data sets, the established models were demonstrated qualified enough to provide reliable predictions to S. aureus growth on spinach for risk assessment purpose. During the modeling process, OH-Fit V1.0 software was applied to simplify the process of establishing predictive models. It has been proved to be a pretty simple and fast tool for predictive modeling investigators and stakeholder.