Tantalum thin films with thicknesses varying from 15 to 250nm were grown on silicon substrates by magnetron sputtering. Surface morphology of the films was investigated by atomic force microscopy. Then the film surface dynamic evolution was analyzed within the framework of dynamic scaling theory. The results show that the growth exponent β is about 0.17 for the films thinner than 50nm and 0.45 for thicker films. With the increase of film thickness，the roughness exponent α increases from 0.24 to 0.69 and remains constant for the films thicker than 50nm. The dynamic surface evolution reveals the growth transition from island coalescence to bulk film growth. Surface islands prefer lateral growth to vertical growth during island coalescence.