The G-functions were introduced to determine the switchabilityofaflowfromonedomaintoanotherindiscontinuousdynamicalsystems.Thegyroscopesystemhasawide spectrumofapplicationsinnavigation,aeronauticsandspace engineering.MinandLuo[15]usedsuchatheorytoinvestigatethechaoticsynchronizationoftwononlineargyroscope systems, and Min [16] applied such a new theory to the generalized projective synchronization of a chaotic gyroscope with a periodic gyroscope, and the analytical conditions of synchronization were developed. The noised gyroscope systems should be synchronized with the expected gyroscope systems.In2013,MinandLuo[17]discussedtheparameter characteristicsofprojectivesynchronizationoftwodifferent motion states of the gyroscope system. For security, function synchronization of two dynamical systems should be considered. Thus, theprojective function synchronization of two gyroscope systems with different motions under sinusoidal constraints will be of great interest. The investigation objectiveistomakeacurrentsystemtosynchronizewiththe expected behaviors in design. Inthispaper, fromthetheoryofdiscontinuous dynamical systems, the necessary and sufficient conditions for the projective function synchronization of two gyroscope systems withdifferentdynamicalbehaviorswillbederived.Fromthe analyticalconditions,theinvariantdomainforthepartialand full, projective function synchronizations will be achieved. Finally, numerical illustrations for projective function synchronization of two chaotic gyroscope systems under sinusoidal constraints will be performed.