Abstract: The Flinn diagram of an isometric grains are divided by lines a=1, b=1,and a=b,and curves a²b=1 and ab²=1 into ten subregions,corresponding to ten different combinations of e_x,e_y,e_z,and strain types.The lines and curves represent the special combination of e_x,e_y,e_z, and strain types.There are altogether eighteen strain types of deformed rocks.We have four equations to express a and b that represent respectively the four quarters divided by the lines a=1/K₁ and b=1/K₂,the equations of a and b depend on the bulk deformation behaviour of rocks.An application of the new diagram to determine the strain of deformed rocks as well as their types is here given.