Online education has become an integral component of our daily routines. Accurately understanding the factors that affect the online teaching ability of secondary school teachers can contribute to enhancing their online instructional performance. This research conducted a survey on the current situation of online teaching ability of teachers in a secondary school in Chengdu. A combination model of entropy weight method and factor analysis method was used to calculate the weight of factors related to teachers' online teaching ability, and an Importance-Performance Analysis (IPA) quadrant diagram was drawn to analyze each ability factor. The results indicated that teachers excelled in nine abilities, including homework supervision, online teaching plan design, and multimedia resource application etc. It is crucial to maintain these strengths going forward. However, there were issues in two abilities, such as the integration of online lesson preparation resources and hardware operation, which required high attention. Finally, four strategies were proposed to enhance teachers' online teaching ability. By doing so, it contributes to a deeper understanding of the key factors influencing online instruction among educators. The research offers several theoretical contributions and practical implications for refining teachers' competencies in online teaching.