According to two estimated relations between the initial period andthe dynamo-generated magnetic dipole field of pulsars, we calculate the statisticaldistributions of pulsar initial periods. It is found that proto-pulsars are very likelyto have rotation periods between 20 ms and 30 ms, and that most of the pulsarsrotate initially at a period ＜ 60 ms. Our result supports the asymmetric neutrinoemission model for pulsar kick.