To address the forming challenges of plastic liners for type Ⅳ hydrogen storage cylinders with large diameter and large length‑to‑diameter ratio，a hot melt welding process with unique low‑cost advantages is adopted to solve the comprehensive optimization problem of weld quality.Taking weld strength and weld morphology as the core optimization objectives，the coupled influence of key process parameters including liner groove size，heating temperature，welding feed speed，and welding feed amount on welding quality is systematically investigated.Through systematic welding experiments，welded pipe specimens are prepared，and their tensile stress-strain curves are tested to evaluate mechanical properties.Combined with macroscopic observation of weld cross‑section morphology and microscopic analysis of fracture structure，the effects of various process parameters on welding forming quality and failure mechanism are revealed.On this basis，the range analysis method is used to comprehensively balance and optimize multiple objectives，and the optimal combination of process parameters is determined：groove size 2.88 mm，heating temperature 252.56 ℃，welding feed speed 1 mm/s，welding feed amount 1.5 mm.This study provides a reliable methodological basis and direct process guidance for the evaluation of hot melt welding process effects and quality improvement of cylindrical plastic liners with large diameter and large length‑to‑diameter ratio.