Something that is moving upstream is moving towards the source of a river against the current, from a point further down the river. Something that is upstream is towards the source of a river.
双语例句
例： Salmon manage to swim upstream to lay their eggs.
三文鱼设法游到上游产卵。
例： the river police, whose headquarters are just upstream of the Ile St Louis.
总部就设在圣路易斯岛上游的水警。