Silage technology can keep fresh fodder for a long time,reduce the loss of nutrients,and is conducive to animal digestion and absorption. The traditional silage technology has disadvantages including low compactness,low anaerobic degree of silage straw,insufficient ammoniation,easy to rot,inconvenient to open and use,inconvenient to seal,inconvenient to transport and so on. Compared with traditional silage,compression packaging silage has better sealing property,less nutrient loss,less secondary fermentation and convenient transportation,which is conducive to promoting the development of silage processing industry. In recent years,the application of compression packaging silage machinery has developed rapidly,but there are few studies on the control of the degree of compaction of raw materials. Therefore,the relationship between the molding height and compression ratio of silage straw compression block,the holding time and the dry and wet state of straw were analyzed. In view of the shortcomings of traditional silage method after crushing green or semi green corn straw,a kind of baler suitable for high compression ratio of silage straw was designed. The compression molding experiments of 4,5 and 6 times compression ratio for the key component compression device of straw baler with high compression ratio were carried out. The optimal compression ratio of 1∶6 was determined by orthogonal design and multilevel analysis. In order to improve the quality of packing forming rate,two hydraulic cylinders were used to open and close the feeding movable cover plate. Two main hydraulic cylinders were used to compress the pressure,one hydraulic cylinder was used to push out and the pressure maintaining box was used to maintain the pressure to complete the compression and pressure maintaining forming. According to the characteristics of a certain degree of expansion and rebound due to stress relaxation after compression,the test of design was conducted. The length,width and height of the pressure retaining box is 600 mm,300 mm and 365 mm,respectively. After verification,the compression device realizes the internal effective working interval of 1 800 mm,600 mm,and 365 mm in length,width and height respectively. It achieves a high compression ratio of 1∶6,which greatly improves the anaerobic conditions,increases the degree of ammoniation,and makes it easy to use.