An andrographis paniculata and a testing method for a preparation thereof, comprising: using a high performance liquid chromatography method to set up a chromatogram of an andrographis paniculata or a preparation thereof, and calculating the content of at least one of the neoandrographolide, the deoxy andrographolide, the dehydroandrographolide, and the neoandrographolide aglycone by using relative correction factors of the neoandrographolide, the deoxy andrographolide, the dehydroandrographolide, and the neoandrographolide aglycone with respect to the andrographolide with the andrographolide being the internal standard. The method of the present invention is highly repeatable, stable, and easy and convenient to operate, and can effectively control the quality of the andrographis paniculata or the preparation thereof.