This research aims to develop a multiple-choice Web-based quiz-game-like formative assessment system, named GAM-WATA. The unique design of "Ask-Hint Strategy" turns the Web-based formative assessment into an online quiz game. "Ask-Hint Strategy" is composed of "Prune Strategy" and "Call-in Strategy". "Prune Strategy" removes one incorrect option and turns the original 4-option item into a 3-option one. "Call-in Strategy" provides the rate at which other test takers choose each option when answering a question. This research also compares the effectiveness of three different types of formative assessment in an e-Learning environment: paper-and-pencil test (PPT), normal Web-based test (N-WBT) and GAM-WATA. In total, 165 fifth grade elementary students (from six classes) in central Taiwan participated in this research. The six classes of students were then divided into three groups and each group was randomly assigned one type of formative assessment. Overall results indicate that different types of formative assessment have significant impacts on e-Learning effectiveness and that the e-Learning effectiveness of the students in the GAM-WATA group appears to be better. Students in the GAM-WATA group more actively participate in Web-based formative assessment to do self-assessment than students in the N-WBT group. The effectiveness of formative assessment will not be significantly improved only by replacing the paper-and-pencil test with Web-based test. The strategies included in GAM-WATA are recommended to be taken into consideration when researchers design Web-based formative assessment systems in the future. (Contains 3 figures and 6 tables.)