This paper discussed the influence of composite rough surface aluminum-doped zinc oxide (ZnO:Al) gratings on light trapping efficiency of thin film silicon solar cells. Rough surface was characterized by correlation length (l_cor) and average height (h_ave), and superimposed on a one-dimension sine ZnO:Al grating with 980 nm period and 160 nm groove depth. The short-circuit current was higher when front electrode AZO grating had smaller l_cor and larger h_ave. As l_cor=0.01, short-circuit current raised with the increase of h_ave value, from 21.93 mA/cm² of h_ave=0.05 to 23.80 mA/cm² of h_ave=0.80. When used as back electrode, the short-circuit current decreased with the increase of h_ave, from 25.50 mA/cm² of h_ave=0.05 to 24.81 mA/cm² of h_ave=0.80. Composite rough surface ZnO:Al grating and non-rough surface ZnO:Al grating were fabricated by chemical etching and direct current sputter respectively. Reflectivity results showed that total reflection of composite rough surface ZnO:Al grating (8.3%) was 1.9% lower than that of non-rough surface ZnO:Al grating (10.2%), and specular reflection of composite rough surface ZnO:Al grating (4.7%) was 2.1% lower than that of non-rough surface ZnO:Al grating (6.8%). Rigorous coupled wave method was used to simulate reflection of ZnO:Al grating with and non- rough surface. Results further confirmed that composite rough ZnO:Al grating was more suitable for front electrode of thin film solar cells due to its better anti-reflection effect and could obtain a larger short-circuit current. Non-rough surface ZnO:Al grating could reflect more photons back to silicon absorption layer due to its higher reflection and was more suitable for back electrode.