  We make statistics about the number distribution of normal radio pulsars
according to the pulsar spin period. And find the physical meaning of the
traditional statistical method about this problem is very limited. According to
the statistical method proposed by us, the distribution rule is exactly the
exponentially decay with the spin period increasing, especially important,
which can be interpreted as normal radio pulsar number decays as the radiative
elements decay. It discloses that though belonging to two different extreme
scales of the universe and having different inner active mechanisms, the normal
radio pulsars and radiative elements accord with the same varying rule. And
like the half decay period of the radiative elements we can also introduce the
half decay spin period of the normal radio pulsars.
