To efficiently convey information and optimise teaching effect, it is necessary to design and develop high-quality online learning materials. To determine the different learning effect of with and without an instructor, this study selects three types of data: test data, eye movement data and questionnaire and interview data. A few primary results of this study are: 1) instructors have no significant impact on learners' conceptual learning grades of declarative knowledge; 2) there is no significant difference in learners' performance of viewing area, but there is a difference in their performance of teachers area; 3) through comprehensive questionnaire and interview data analysis, there is no significant difference in learners' learning experience of conceptual learning in declarative knowledge video with and without an instructor. This study provides a reference for designing and developing online video lectures. When designing the video lectures of conceptual learning, it can adopt instructor-free way considering saving time and cost.