Among all kinds of modern packaging bags, liquid packaging bags have a relatively large market and play an indispensable role in the daily life of consumers. From soybean milk for breakfast, to juice in the afternoon, to milk before bed, and even the packaging of stone oil packed by Arab Dubai local tyrants, all belong to the category of liquid packaging. Because of this, the demand for liquid packaging is very large, and it is the most important form of order for flexible packaging enterprises. In the past, liquid packaging was mainly made of self-supporting bags and penguin bags. However, with the continuous improvement of consumers’ requirements for the appearance and performance of packaging and the development demand of the whole market, more and more large food and beverage enterprises have chosen the flat bottom bag packaging form in the past two years. Among them, the most popular is the octagonal flat bottom bag liquid packaging. Because it is both beautiful and practical, it is deeply loved by the majority of consumers. The square bottom bag for liquid packaging is the mainstream of the market and the favorite of food enterprises. If flexible packaging enterprises can improve the production efficiency and yield of square bottom bags for liquid packaging, they will effectively enhance their competitiveness in the industry. The square bottom bag displays five sides and has more space than the self standing bag penguin bag to meet customer needs. The square standing bottom makes full use of the shelf space, which is in line with the development of large market supermarkets. Liquid packaging has high requirements for sealing performance and heat sealing strength during bag making. When composite bags with different structures are used, different heat sealing temperatures, heat sealing pressures and heat sealing times need to be set. Once the operation is wrong, the product will become a waste product, and the waste rate will rise, and the cost of bag making will also increase accordingly. Therefore, it is necessary for flexible packaging enterprises to understand the performance characteristics of composite bags, operate relevant bag making machines skillfully and deal with problems in the production process in a timely manner.