With utilization of internals to enhance heat transfer and regulate the pyrolysis gas flow direction inside the reactor, this study proposed and tested a new fixed-bed coal pyrolysis reactor indirectly heated. Majorly, both yield and quality of the produced tar were evaluated by comparing the behaviors of laboratory pyrolyzers with and without internals. The results show that the use of the particularly designed internals increased the heating efficiency from the reactor wall to the coal bed by more than 2 times, while the tar yield was obviously higher in the reactor with internals. For Yilan sub-bituminous coal, the tar yield reached about 80% of the tar yield given by the Gray-King analysis (11.8 wt %, dry-coal basis) in the laboratory reactor with internals, while the corresponding light tar below the boiling points of 360 degrees C was about 65 wt % of the total tar mass. With raising the heating temperature of the furnace from 600 to 1000 degrees C, the tar yield increased from 8.5 to 10.64 wt % for the reactor with internals. In contrast, the tar yield, decreased remarkably from 7.98 to 4.77 wt % in the conventional reactor without any internal. All of these show essentially that the adopted internals greatly changed the physiochemical procedure involved in coal pyrolysis, which, in turn, obviously affected the yield and quality of tar.