Ohmic contacts with low resistance and low barrier height were fabricated on n-type GaN films using W metallization. The n-type GaN films were grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD) with Si as the dopant. Ohmic characteristics were studied for GaN films with Si carrier concentration varying from 1.4 × 1017 to 1.8 × 1019 cm-3. The specific contact resistivity were reduced with increasing Si-doping concentration on as-deposited W/GaN films, and the lowest value was 3.6 × 10-4 Ωcm2 on n-type GaN with a concentration of 1.8 × 1019 cm-3. After rapid thermal annealing (RTA) treatment on W/GaN films at 1000°C for 30 s, the specific contact resistivity were reduced to 1 × 10-4 Ωcm2. The W metal on n-type GaN films, show that good thermal stability varied the annealing temperatures. The barrier height of as-deposited W metal on GaN is calculated to be 0.058 eV.