A novel solid polymer electrolyte with comb-like structure is prepared via a solvent-free UV-cured method. The relationship between conductivity and molecular weight is investigated and revealed. The optimal electrolyte presents a considerably high conductivity of 1.44 × 10⁻⁴ S·cm⁻¹ at 30 ℃. Meanwhile, it shows excellent compatibility with metallic lithium and wide electrochemical window (> 5 V). To investigate the safety and cycling performance, the coin cell and soft package battery are assembled respectively. The LiFePO₄/Li coin cells exhibit initial discharge specific capacities of 163.2, 147.7, 137.3 and 108.7 mA·h·g⁻¹ at 0.1, 0.2, 0.5 and 1C under 60 ℃, respectively. Notably, when the coin cells work at 30 ℃, the initial discharge specific capacities at 0.05, 0.1, 0.2 and 0.5C are 140.5, 133.5, 107.7 and 55.6 mA·h·g⁻¹. Significantly, a 3.5 cm × 7 cm solid-state soft pack battery is fabricated and cycling at 30 ℃. The first discharge capacity reaches to 137.5 mA·h·g⁻¹ and the capacity retention is as high as 84.4% after 100 cycles at 0.2C and remain 95.5% after 100 cycles at 0.5C, respectively. These results shows a promising solid polymer electrolyte for solid-state batteries with good cycling and safety performance.