Abstract: Let the area covered by Mises yield locus on the π-plane be equal to the area coverage of a non-equiangular but equilateral dodecagon and the two areas be overlapping to determine the six apexes of the new yield locus. Then, the lines connecting these apexes and six inscribed points are defined as the new yield criterion loci or locus as a whole. The linear equation of the new locus in Haigh Westergaard stress space has been deduced. It is proved that the new yield locus is approximate upmost to that of Mises yield criterion and is called MA(mast adjacent) yield criterion for short, and the apex angle of the new dodecagon is 159.836° with the apex angle of circumscribed hexagon equal to 140.164°. The mean error of deviator stress vector modulus on the π-plane between Mises and MA criterions is zero. Furthermore, the plastic power rate for unit volume is also given.