Abstract: In this paper we present some new investigations on the transverse spin of evanescent waves and obtain the following results: 1) the quantization form of the transverse spin is revealed; 2) from a unified point of view, the transverse spin can be attributed to the presence of an effective rest mass of evanescent waves; 3) the transverse spin can also be described by the spin matrix of the photon field; 4) unlike a free optical field in vacuum whose spin projection on the propagation direction is the only observable, owing to the effective rest mass, the spin projection of evanescent waves on other directions is also an observable, such that one can develop an optical analogy of spintronics, i.e., spinoptics.