In recent years some research results about earthquake prediction by means of seismological methods show that we can achieve some successes of predicting strong earthquakes by use of preparation gaps. First, we can draw primary gaps on the epicenter distribution pictures on small earthquakes. Then we find out the preparation gaps based on some criteria and evaluate the magnitude, time and location of future earthquake from emperical formulars. But we will meet the problem of false prediction of earthquake. In this paper we study the false prediction of earthquake by applying preparation gap. It is found that unload earthquakes occurred in the neighborhood of a preparation process of earthquake. So that no following earthquake will occur within the preparation gap. we sum up some characteristics of unload earthquakes and evaluate the effects to reduce false palse prediction of earthquakes from them. It is possible that the unloading role may be used to explain the phenomena of other precursors of no following earthquake.