Hi 승표,
It's not really an offset. The Integrator block parmameter 'Initial Condition' is set to zero, which corresponds to setting the constant of integration C = -1 in the solution for the antiderivative. Double click on the Integrator block and set the Initival Condition parameter to whatever is needed to get the desired result.
Another way to think of it is that the output of the Intregator block is: x0 + int(-sin(tau) dtau, from 0, to x)
(thought it it looks like your actual, input sine wave is at a higher frequency).
