For the need to release trappedoil pressure in external gear pumps with involutes gear pairs. Firstly, compared with current rectangleshaped relief groove, and based on the different trappedoil characteristics and relief measure in double meshing teeth range from single meshing tooth range, a new double obliqueshaped profile with larger relief area and simple processing was proposed for trappedoil relief, then it’s construction was described, its shape and location dimensions was designed in detail. Secondly, by the 3D model rotating method and area measurement method, all dynamic relief areas of each different meshing position were measured. Thirdly, form the trappedoil process cycle and a created simple emulating model, different trappedoil pressure simulation calculations in double meshing teeth range from single meshing tooth range, was respectively executed in different grooves with double obliqueshaped from rectangleshaped. All results indicated that relief area was greatly enlarged by the new double obliqueshaped relief groove than current rectangleshaped relief groove, among them, the maximum relief area in double meshing teeth range was enlarged by 1.17 times, by 11.7 times in single meshing tooth range; the maximum trappedoil pressure in double meshing teeth range was decreased by 46.2% and only was 4.3% more than discharge pressure, and by 60.2% and only was 1.6% in single meshing tooth range, which could be considered as a no trappedoil phenomenon; and each profiled outlines of double obliqueshaped relief grooves on both sides of suction oil and discharge oil was enclosed by 5 straight line segments and 3 circular arc segments with ø2.0 mm, which could be considered as a simple structure and an easy processing, etc. It is concluded that a new design approach to relief groove is provided for gear pumps.