Abstract: The demand for "miniaturization and high reliability" of antennas in on-board communication systems is increasingly stringent. Traditional fixed-size quadrifilar helical antennas (QHA) fail to meet the on-board requirements due to their large deployment height and excessive envelope. This paper takes the helicon of the on-board deployable helical antenna as the research object, and carries out the design around the core goal of "no yielding in retraction and compression, and stiffness maintenance in the deployed state". First, based on the mechanical theory of helical spring structures, a parameter mapping model of "working state - free state" is established. With the constant deployed length as the constraint, the calculation methods for the mean diameter, pitch and helix angle in the free state are derived. Second, focus on the problem of reduced stability caused by the large helix ratio, a scheme of "conformal cable pre-tightening + incomplete deployment" is proposed, which balances the stiffness and yield risk through pre-tightening load. Finally, an innovative process combination of "mold forming + furnace heat treatment + heavy pressure treatment" is adopted to solve the problem of dimensional precision. Experimental verification shows that the four helicon made of beryllium bronze do not undergo yield deformation in the retracted state, the deployment repeat accuracy is less than or equal to 1 mm, and its fundamental frequency in the expanded state is greater than 1 Hz, the product meets the application requirements.