The general purpose of this study is to investigate the best fit model for the ability of students in technical writing that used structural equation modeling (SEM) as the basis for the design of the instrument in analyzing the relationship between affective factors, teacher communication behavior, vocabulary learning strategies and technical writing competency. A descriptive-causal design and stratified random sampling technique were used to select 400 students. Four questionnaires were used to collect data through an e-survey. Mean, standard deviation, Pearson product-moment correlation and multiple regression analysis were also used to analyze the data collected. It was found that all the variables are at a high level which means that the respondents are often exhibiting them. The affective factors, teachers communication behavior, and vocabulary learning strategy have a significant relationship with students competency in technical writing. The most appropriate technical writing competency model is model 5 with attitude and skill indicators. Motivation and self-confidence are indicators of the affective factor. Challenging, encouragement and praise, understanding and friendly are the teachers behavior in communication. Vocabulary learning strategy with cognitive, metacognitive, memory, and determination indicators. It only indicates that the affective factor, teachers communication behavior, and vocabulary learning strategy plays an important role in students technical writing competency.