A quantifiable pneumatic valve dynamic stability judging method includes the steps of firstly, using lumped parameters to build a pneumatic valve dynamic model; secondly, linearizing the pneumatic valve dynamic model through infinitesimal perturbation analysis to obtain a linear homogeneous equation set of each parameter; deriving pneumatic valve dynamic stability determinant |A|=0 according to exact-solution conditions of the linear homogeneous equation sets; fourthly, solving the determinant |A|=0 to obtain characteristic roots of the pneumatic valve dynamic stability determinant; fifthly, judging pneumatic valve dynamic stability according to the characteristic roots, if real parts of all the characteristic roots are negative, judging a valve to be stable, and if positive real parts exist in the characteristic roots, judging the valve to be instable; wherein the larger the positive real parts in the characteristic roots are, the more instable the valve is, and the smaller the negative real parts in the characteristic roots are, the more stable the valve is. The method is applicable to pneumatic valve stability quantifiable judging and stability margin design of valve products, and work reliability of pneumatic valves can be increased.