The study builds on a newly modified Technology Acceptance Model (TAM) to substantiate the motivation and operation of teachers' utilization of online learning resources. A "Comprehensiveness" construct is proposed in the modified TAM to reflect the breadth and depth of rich online knowledge. This new construct serves as the mediator between "Usefulness" and "Behavioral Intention" in the new TAM structure. In addition, the "Ease of Use" factor in conventional TAM is proposed to moderate the mediation in the modified TAM. Survey data are collected from 301 teachers undertaking certified training in Macau and Structural Equation Model (SEM) technique is used to assess the model. Moderated mediation is evaluated using both multi-group bootstrapping method and moderated path analysis method. Both methods verify the presence of moderated mediation with partial mediation in high Ease of Use values and full mediation in low Ease of Use values. Theoretical implication of the current study extends the coverage of TAM applications and academic implication suggests the strengthening in teachers' professional development and government sponsorship in building repositories of online resources.