Abstract: The density of straw briquette can reach 1. 2～1. 4g/cm³ after hot compression of straw. The combustion performance of the briquette is much superior than that of firewood and similar to that of common soft coal. Its combustion efficiency can increase by about 100% over that before compression. It is a kind of high grade energy resources which is easy to be transported and stored. This paper makes a preliminary study on the briquette formation and proposes a mechanical model of the pressure distribution of raw material in the process of spiral extrusion. Coefficients of combustion performance of straw briquette are also studied and analysed.