The concrete block mattress is an economic and efficient mean for erosion protection,which is used widely in river bank protection projects and waterway protection projects,and also applied in some ocean engineering with poor wave and current conditions.The force on the block under action of wave and current is analyzed firstly,then series physical model tests about the stability of three concrete blocks with different thickness are carried out under three hydrodynamic conditions,ie.under the action of current singly,under the action of wave singly,and under the co-action of current and wave.The maximal current speed and the maximal wave height are measured in the tests,and the results of experiment are analyzed and discussed.This research provides reference for other similar engineering projects.