The chaotic character of a Bose-Einstein condensate in titled optical lattices is investigated. A perturbation solution of the Gross-Pitaevskii equation is obtained by using the direct perturbation method. Theoretical analysis reveals that the perturbation solution is chaotic one because it satisfies the Melnikov chaos criterion, which indicates the system existing chaotic behavior. The corresponding numerical simulation results confirm the theoretical results. However, the chaos of the system can be controlled by adjusting the system parameters or changing the initial conditions, which shows the system parameters or the initial conditions play a very important role in control chaos.