Phosphorus-based polymers have gained much interest in recent years due to the phosphorus atoms that impart polymers interesting properties. Thus, the synthesis of phosphorus-containing polymers in practical and feasible ways is highly desirable in synthetic polymer chemistry. In this study, we report a new method based on the ultrafast thiol-yne reaction between dithiol-functionalized phosphothioester compounds and electron-deficient alkyne compounds to prepare phosphorus-containing polymers. For this purpose, two dithiol-functionalized phosphothioester compounds were synthesized and reacted with seven structurally different electron-deficient alkyne compounds in chloroform (CHCl3) in 1 min using an organocatalyst, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). The polymerizations proceeded successfully and fourteen phosphothioester-containing polythioethers were achieved with reasonable molecular weights and high yields. The resulting polymers were characterized in detail by NMR, GPC, and DSC measurements. Given the above-mentioned demands in the preparation of phosphorus-containing polymers, the proposed approach in this study offers a rational, robust, time- and energy-saving solution to this aim. More importantly, the proposed method does not require harsh conditions, metal, acid, or base additives.