Preparation of hydrogenated tetrahedral amorphous carbon (ta-C:H) films with good mechanical properties by plasma-enhanced chemical vapor deposition (PECVD) is expected to meet requirement in industrial application. This paper reported the microstructure and mechanical properties of (ta-C:H) films prepared by a self-designed PECVD technique. As the bias voltage varies from -200 V to -500 V, the hardness and elastic modulus first decrease and then increase, reaching the maximum values of 34.0 GPa and 282.0 GPa respectively. The evolution of compressive stress with bias voltage shows a similar trend. In this case, the hardness and elastic modulus of films prepared by the self-designed PECVD technique both are improved, compared with those by the conventional PECVD methods. The mole fraction of sp3 hybridized bond is greater than 62.3% when the bias voltage changes from -200 V to -500 V. Carbon films were deposited using the self-designed PECVD technique, showing the typical characteristics of ta-C:H films. This can be attributed to the increased ion bombardment and ionization due to the incorporation of a water-cooled radio frequency double helix electrode and a plate electrode resulting in an enhanced sp3 content. This paper provides a promising technology to fabricate ta-C:H films with high hardness and elastic modulus for industrial applications.