The rumor as a universal social phenomenon，along with the popularity of the Internet，network communicators anonymity，disinformation low cost，convenience，spread rumors about the influence.According to a Sina microblog rumor that stretching out one’s hand can touch it when watching 3D Titanic，the microblog，variability，and diffusion of rumor breeds to resolve the four propagation path are analyzed，and then draw propagation causes include information itself，grassroots disseminator，individual audience，commercial media，the spread of rumors of microblog in dual roles paradox of deep reflection.