Implementing an effective teaching and learning process with the integration of online learning platform is important for the teachers, in order to maximize the online teaching and learning situation. In this case, this study aimed at investigating the constraints found in SMA Negeri 1 Kediri in preparing lesson plan through Google Classroom. The researcher chosen SMA Negeri 1 Kediri in Tabanan Regency, Bali. In SMA Negeri 1 Kediri, Google Classroom is one of the most frequently used platforms based on the result of the pre-observation stage. Based on the pre-observation, it was found that a lot of the student have used smartphone, especially 11th grade students, which is related to the current situation (online learning). This study uses qualitative design as the design of the study, with the qualitative data as the results. The data of teachers’ constraints in preparing lesson plan are collected by using questionnaire consisted of 20 items, in which the questionnaire related to the 5 aspects of lesson plan, such as: 1) constraints in the aspect of learning objectives, 2) constraints in the aspect of learning materials, 3) constraints in the aspect of learning activities, 4) constraints in the aspect of learning media and sources, and 5) constraints in the aspect of learning assessment. As the result, it was found that there are some constraints found, such as: 1) the online learning media is only an intermediary for students in collecting their work, 2) the online learning media that only used to submit assignments, 3) the difficulties in judging the actual work of students from these activities, 4) the online learning platform which is only used to convey material, and 5) the assessment types and techniques cannot be clearly assessed from these activities. Thus, the observable problems found has to be solved by the teacher through mastering the five aspects of lesson plan, in order to be adapted with the dynamic teaching and learning situation.