【Abstract】This paper analyzes the common problem existing in English online course： The text message， rather than the learning activity， is the focus of the course design； the language input is emphasized， yet the learning activity is ignored. Based on the activity-based theory， Krashen’s input hypothesis and Swain’s output hypothesis， with the case study， the author elaborates how to make the input-based online activity comprehensible with PI model， and with PPP model， how to make the output-based online activities effective for English acquisition while designing the English online course.
　　【Key words】online English course design； activity-based； input hypothesis； output-hypothesis； PI model； PPP model
　　Introduction
　　Nowadays， the online English courses are growing in both popularity and offerings. The online English course offers convenience for the learners because it can facilitates long distance exchanges， both synchronous and asynchronous task， and students publishing， etc. However， recent surveys demonstrate that some online English courses are ineffective due to the ignorance of the learning activity and interaction. Another problem occurring in some online English course is that the language input is emphasized， yet the output is neglected. Since the fundamental nature of learning is engagement in activity （Prince， 2004）， the learning activity should be given the priority in designing an online English course. Based on the activity-based theory as well as the input and output theory of second language， this paper aims to explain how to make input-based and output-based activities effective for second language acquisition in designing the online English course.
　　Literature review
　　Activity-based learning
　　Activity-based learning as defined by Prince （2004） is a learning method in which students are engaged in the “learning processes. According to Hardfield， Davies， Hede， Panko Kenley （2007）， in Activity-based learning teaching method， students actively participate in the learning experience rather than sit as passive listeners. Learning activities if based on “real life experience” help learners to transform knowledge or information into their personal knowledge which they can apply in different situation （Edward， 2001）. Marilyn and Higgins （1997） define activity-based learning as the learning process in which “student is actively involved in doing or in seeing something done.” According to them activity-based teaching method “frequently involved the use of manipulative materials.” According to Churchill （2003）， activity-based learning helps learners to “construct mental models that allow for “higher-order” performance such as applied problem solving and transfer of information and skills.” Activity-based learning theory is a cognitive-learning theory which is basically a “constructivist” learning theory （Hein，，1991）. According to constructivist view of learning， each person construct their own knowledge and learning process based on previous experience. According to constructivism， teachers cannot transfer their knowledge to the students （Domin， 2007）. For meaningful learning to be taken place， learners require to experience an event.