Linear low density polyethylene (LLDPE) excellent environmental stress crack resistance, chemical inertness, low temperature impact, strength and resistance to ultraviolet exposure, rigidity, toughness combined with a low density, good moldability and reasonable price have attracted attention as potential matrix for natural fibers reinforced composites. Hemp plants as cost effective, renewable, high productive, low density and CO2 neutral, biodegradable resource are investigated intensively for a range of applications. As our previous investigations show, the best mechanical properties without hemp fibres pre-processing were achieved with 30 wt% fibres reinforcement and with water sorption capability after 240 h in a range from 7.1 to 8.8 wt%. In present research with hemp fibres (length up to 1 mm) reinforced LLDPE (grade LL 6201) matrix composites with hemp fibres content in a range from 30 to 50 wt% with four different pre-processing technologies were produced and such their properties as tensile strength and elongation at break, tensile modulus, melt flow index, microhardness and water absorption dynamics were investigated. Capillary viscosimetry was used for fluidity evaluation and melt flow index (MFI) evaluated for all variants. MFI measurements for composites with hemp fibres content 30 wt% depending on pre-processing technology applied gives values in a range from 0.75 g/10min. to 16.76 g/10min. which are sufficient to process these composites with traditional polymer processing methods (extrusion, compression moulding). In distinction from our previous studies, MFI of two present variants with fibers pre-processing were high enough to increase hemp fibers content from 30 to 50 wt% with moderate increase of water sorption capability.