ZNN-D6 is manufactured to test rheological parameters in accordance with API. It can measure various rheological parameters. Draw rheological diagram according to multi-point measurement value, determine fluid model of liquid in the flow process, then select suitable formula and measure non-Newtonian fluid model. Meanwhile, it can test yield point, gel strength, consistency coefficient and flow behavior index and so on. The instrument applies to research and analysis of drilling fluid rheological parameters. Easy operation and accurate testing can meet safe and quick drilling requirements.