This paper focuses on the uniform boundary estimates in homogenization of a family of higher order elliptic operators L ε , with rapidly oscillating periodic coefficients. We derive uniform boundary C m−1,λ (0 < λ < 1), W m,p estimates in C 1 domains, as well as uniform boundary C m−1,1 estimate in C 1,θ (0 < θ < 1) domains without the symmetry assumption on the operator. The proof, motivated by the profound work "S.N. Armstrong and C. K. Smart, Ann. Sci. Éc. Norm. Supér. ( 2016), Z. Shen, Anal. PDE (2017)", is based on a suboptimal convergence rate in H m−1 (Ω). Compared to "C.E. Kenig, F. Lin and Z. Shen, Arch. Ration. Mech. Anal. (2012), Z. Shen, Anal. PDE ( 2017)", the convergence rate obtained here does not require the symmetry assumption on the operator, nor additional assumptions on the regularity of u 0 (the solution to the homogenized problem), and thus might be of some independent interests even for second order elliptic systems.