Although fuzzy tasks are ubiquitous in the organizational context，researches focusing on informational organization structures that supports fuzzy tasks in online group discussion have been lacking． An analysis from the perspective of task-technology fit indicates that traditional linear structure or tree structure cannot well support fuzzy tasks． To well support the fuzzy tasks，in this study we propose a new lineartree structure that provides a high level of support in the perspectives of communication，process structuring，and information processing． We also design an experiment to validate if the proposed information structure will lead to increased performance for fuzzy tasks． The results indicate that for fuzzy tasks，using a groupware with lineartree structure will lead to higher decision efficiency，higher decision quality and higher satisfaction with the decision process．