Any project always gives effects to the environment, neither good nor bad effects, and so does in weir project. Weir project will give the advantage for communities which have interest with it. If there is any disadvantage, it is commonly a sedimentation problem. But there is a negative impact that is not less important, the lost of some fish species. Some kinds of fish have habit to migrate from downstream to upstream of the river and the other way. A weir is a permanent construction that crossing the river. The existence of this construction will block the migration process of fish. Therefore, it is important to provide a passage for fish to migrate in designing a weir, such as a fish ladder, fish passage and fish track. This study will examine the advantage of fish ladder or fish passage for the sustainable of river ecosystem and the design which is much appropriate with the condition of weir in Indonesia.