本研究的目的，是在實作一個以開放式問答題的作答方式為基礎的線上輔助學習系統，藉以提升評量及學習的效果。我們選定的問題領域在地球科學，以極光的發生為例，將問題所涉及的觀念進一步拆解細分成許多小觀念，建立階層化使用者知識模型，以評估學生於各個觀念的分別表現。學生於作答時，系統會即時分析學生的答案，以評估學生在各觀念的表現，並在適當的時機提供回饋，嘗試協助學生思考原本未能答好的觀念。我們以不同的回饋時機及回饋內容為獨立變因，嘗試瞭解對使用者答題表現的影響。我們也以個案分析的方式將學生的對於系統學習態度分類，藉以瞭解不同類型學生對此類系統的接受程度。我們認為此系統可以提供學生作答歷程予教學者進行分析，用以找出學生缺漏的觀念，進而協助提升教學效果。 / The purpose of this research is to use an open-ended based on-line learning system to improve the effects of evaluation and learning. We set the question domain at Earth Science. Taking the occurrence of polar lights, we divide the related concept into many small concepts, and build the hierarchical user knowledge model to evaluate student’s reactions to each concept. While students take the test, the system will analyze the answers to evaluate the students, and provide feedbacks timely to help the student think over the missing concept. Taking the different feedback timing and feedbacks as independent factors, we try to understand the influence to the users’ performance. By using case study, we classify the students’ learning attitudes to understand the different types of students’ acceptance of this system. We think that this system can provide student’s answering process to teachers for analyzing. By using this, teachers can find out students’ missing concept and to provide teaching effectiveness.