The Cauchy problem of the modified Camassa-Holm (mCH) equation with initial data $ u(0) $ that are analytic on the line and have uniform radius of analyticity $ r(0) $ is considered. First, by using bilinear estimates for the nonlocal nonlinearity in analytic Bourgain spaces, it is shown that this equation is well-posed in analytic Gevrey spaces $ G^{\delta, s} $, with useful solution lifespan $ T_0 $ and size estimates. This shows that the radius of spatial analyticity $ r(t) $ persists during the time interval $ [-T_0, T_0] $. Then, exploiting the fact that solutions to this equation conserve the $ H^1 $ norm, and utilizing the available bilinear estimates, an almost conservation low in $ G^{\delta,1} $ spaces is proved. Finally, using this almost conservation law it is shown that the solution $ u(t) $ exists for all time $ t $ and a lower bound for the radius of spatial analyticity is provided.