A series of Pt-bearing dealuminated USY supported Cs salts of 12-tungstophosphoric acid (PW) catalysts were prepared and their catalytic performances were measured in the hydroisomerization of n-heptane with an atmospheric fixed-bed flow reactor. USY was found to be a poor support for Cs salts of PW, leading to a lower catalytic activity in this reaction, but dealuminated USY supported Cs salts of PW catalysts showed very high catalytic conversion and selectivity. Among the various Cs salts of PW with different Cs/P ratios, Cs2.0PW was revealed to be the most effective active species. Over the dealuminated USY supported catalyst with the Pt loading of 0.4 wt.% and Cs2.0PW loading of 10 wt.%, the conversion of n-heptane was enhanced up to 76.2% with a high selectivity to isomerized products of 92.2%.