Methoxylation of commercial citrus pectin in anhydrous methanol catalyzed by HCl was conducted. Reaction conditions including reaction time, temperature, solid-to-liquid ratio (SLR) and HCl concentration were investigated and optimized. High methoxyl pectins with various degree of methoxylation (DM) of >90% were obtained. Results of molecular weight distribution showed that DM was improved with the increase of reaction temperature, reaction time and acid concentration, but the number-average molecular weight was decreased. Particularly, HMP with DM of (91.20±0.13)% was obtained under SLR 1∶50 (w/v) at 60 ℃ with 0.1 mol/L HCl for 12 h, and the Mw was decreased to 15.00 kDa. Furthermore, extremely high DM emulsification properties were studied due to its amphiphilic property (by hydrophobic methoxyl groups and hydrophilic hydroxyl groups) and short molecular length. Nano-emulsions with φ (oil)= 10%-30% were prepared by high energy method (high speed shearing) and their 7-day stability, Zeta-potential and particle size were characterized. Emulsion of 3 500 nm with good stability was produced by high methoxyl pectin with DM of 91.20%.