Analysis of the geophysical,planetary-geochemical and high pressure and temperature experimental data indicates that plenty of fluids exists in the mantle. In this paper,some hypotheses of fluid-induced earthquakes were briefly introduced and the prospects were suggested. The data of the fluid samples in mantle rocks,water-bearing high-pressure phases of silicate and geophysical exploration indicate that fluids exist in the whole mantle,mantle transition zone among which D″ layer are enriched in the fluids that are high energy density,and total amount of water in the mantle is estimated being several magnitudes higher than that of sea water on the earth. Thermal convection caused by migration of the high energy density fluids results in heterogeneities of temperature,seismic wave velocity,electrical conductivity and chemical compositions in the solid earth. The upwards migrating fluids alter the physical and chemical properties of the crust and mantle rocks,and provide huge amount of heat energy for producing magma and earthquake. The functions of mantle fluids in the earthquake generation involve two aspects that are inducing earthquake by reducing friction between two walls of a fault,and producing earthquake by explosion or phase transfer of the fluids. The cryptoexplosive mechanics means that the high energy density fluids derived from the core and mantle migrate repeatedly in the way of episodic penetration-inflate-cryptoexplosion cycle,resulting in different types of earthquakes at the different depths. However,more work should be done further to understand both behavior of mantle fluids and their role in earthquake generation.