Despite the growing interest and increased demand for the development of biodegradable recyclable materials, the use of thermoplastic composites highly filled with natural fibers is not widely used in industry. This is due to the fact that such composites generally have lower strength compared to thermosetting composites. However, they have the advantage of providing product flexibility and improved biodegradability characteristics. Composites made of thermoplastic polymer matrixes to which hemp fibers are added, characterized with good mechanical properties. The research focused on the effectiveness of injection moulded polymer composites reinforced with hemp stems. Computer simulation of composites injection was performed, where the reinforcement content is within 30-40%. In order to achieve the expected results of the tests, it is necessary to modify the injection mould and use wider channels supplying the material to the moulding cavity. In order to examine the results of the simulation tests, verification tests were carried out with the use of testing machines. In the result it has been found that the mechanical properties of these materials increase whilest hemp fiber content are increased. Composites with 40% reinforcement showed good performance, suggesting their potential for use as an environmentally friendly alternative material in automotive or electronics.