In this paper, we consider the convergence problem of Kawahara equationut+α∂x5u+β∂x3u+∂x(u2)=0 on real line with rough data. Firstly, by using Strichartz estimates as well high-low frequency idea, establish two crucial bilinear estimates, which are just Lemma 3.1, 3.2 in paper; also present proof 3.3 shows that s>−12 is necessary for 3.2. Secondly, truncated technique and technique, show pointw...