二者意思不同，用法也不同。

take steps : 采取措施（含有有步骤的做…事）例句：The boss decided to take steps to reduce the production cost .(老板决定采取措施降低生产成本。）Local governments took positive steps to stimulate the housing market.(今年地方政府采取积极措施来刺激房产市场。take a step : 采取措施 ，走一步，迈出一步Take a step back and there will be a bigger world in front of you.(退一步海阔天空。）