Based on the linear stability analysis, the modulational instablilities (MIs) of two-component Bose-Einstein condensations (BECs) in the optical lattices are studied, especially the relation of MI with the different component and modulational wavevectors, and with the inter- and intra- interaction when the condition of atom current conversation is not satisfied. The results show that when the condition of atom current is not satisfied, the new MI areas of two-component BEC in the optical lattice with the component wavevectors, modulational wavevectors and the interaction between components can arise. The above results can gives us some useful information about manipulating two-component BECs in practice.