A novel photografting, non-vapor and non-liquid phase method was developed to functionalize low-density polyethylene (LDPE) powder. The structure and adhesion properties of LDPE grafted with methacrylic acid (MAA) by this method were studied by Fourier transform infrared (FTIR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM) and water contact angle, peel strength and graft degree measurements. The results show that the chemically inert LDPE powder can be graft-copolymerized with MAA via this non-vapor and non-liquid phase photografting method. The graft degree increases with the ultraviolet irradiation time. The hydrophilicity of the grafted LDPE powder and the peel strength of high density polyethylene (HDPE)/steel joint with the grafted LDPE powder used as hot melt adhesive are improved considerably as compared to that with the ungrafted LDPE powder.