Microplastics are an emerging marine pollutant, and their negative impacts on the photosynthetic efficiency of marine photoautotrophs are gradually endangering marine ecosystems and biota. To analyze and solve the impact of microplastic particles on light propagation in the ocean, the investigation of radiative properties of microplastic particles is essential. The extinction and absorption coefficients of polyamide-12 (PA12) with different particle concentrations are experimentally measured using transmission and integration methods in the spectral range of 200 to 1100 nm. The extinction and absorption cross sections are obtained from the measured extinction and absorption coefficients. The measured PA12 absorption peaks, located at 692, 728, 764, 835, and 940 nm, correspond to the vibrational absorption of methylene groups (-CH₂) and amide groups (CO-NH). The scattering albedo of PA12 is mostly above 0.7 in the visible spectral, indicating that PA12 is a scattering dominated medium. The measured radiative properties of PA12 provide optical parameters for determining the radiative transfer containing microplastics.