Active filters have been a cornerstone of electronic engineering since their inception in the mid-20th century. As technology has advanced, these components have become increasingly sophisticated and integral to a wide range of applications, from audio equipment to telecommunications. This article introduces two types of active filters, active low-pass and active high-pass. Active filters play a vital role in modern electronic and communication systems. They can enhance signals, which is very important in signal transmission and processing. Active filters are very flexible in design and can achieve a variety of filtering functions. The circuit design can also be adjusted by adjusting the parameters of the filter. The composition and basic principles of the two active filters are briefly explained, as well as why we use active filters in circuits. Secondly, we explain the composition of highorder active filters and give a schematic diagram. Finally, this article explains the roll-off rate, design equations and transfer function of the Butterworth filter, describes the practical application of Butterworth and the shortcomings of the Butterworth filter.