Abstract: For analysing cutting-gas, the authors designed and set up a degassing apparatus that agitates and crushs cuttings. It is used together with HP-5880 GC for qualitative and quantitative determinations of cutting-gas. Through experiments under various conditions, the performance of the apparatus has bee a proved to be good for rock sample crushing and degassing. The method employed is reliable and the data obtained are comparable to each other.During experiments, optimum operation conditions were selected and determined: (1) grain size of rock sample. 2-8mm; (2) the amount of rock sample: 10-15g; (3) agitating medium: distilled water; (4)agitating time. 8 minutes; (5) top volume of degassing cylinder: 5-9ml; (6)balance time for diffusion. 5 minutes.