High deep clastic reservoir of Hailar Basin is high of tuffaceous composition,and the analysis of microscopic shows that reservoir space is based on the secondary porosity formed by dissolition of the carbonate cements and feldspar minerals.The article mades a dissolute experiment of the cast thins made by the tuffaceous sandstone,observes and compares the changes of mineral association and pore space, studys thedissolution mechanization of tuffaceous sandstone, make scientific contribution to the prediction of high quality reservoirs