Abstract: In addition to hydrocarbon liquid (HCL) and CH 4, flash pyrolysis of bituminous can also produce char, tar and water. There is residuary volatile (RV) in char. The RV in char produced in H 2 atmosphere is lower than in that produced in N 2 atmosphere. The RV content in char is a criterion of flash pyrolysis degree. The main reason of the fact that the density of char produced in H 2 is only 1/3.5 of that of coal is that active char reacts with H 2 to produce CH 4. The yield of HCL is related to yield of tar. The secondary hydrogenization of tar is the principal procedure to produce HCL. The pyrolysis water produced in H 2 atmosphere is more than that produced in N 2 atomosphere. The main procedure to produce water is hydrogen in gaseous phase to combine oxygen in coal.