Literature review shows that GSS generally fails to increase group consensus and satisfaction. The reasons for this failure are not fully known. This research investigated this issue from an influence process perspective. The independent variables were support (computer support versus non-computer support,) and task type (intellective task versus preference task). The dependent variables were three influence process variables (informational influence, normative influence, and influence distribution) and three outcome variables (consensus, decision satisfaction, and decision process satisfaction). The findings suggest that the failure, from influence process perspective, may be attributed to the "offset effect of GSS". In preference task, the increased part of group consensus and satisfaction, due to that GSS increased influence distribution balance, were offset at the same time by the decreased part, due to that GSS attenuated normative influence. Likewise, in intellective task, the increased part of consensus and satisfaction, due to that GSS enhanced informational influence, were offset at the same time by the decreased part, due to that GSS decreased influence distribution balance. The implications for the offset effect is discussed.