Aquatic and land plants as well as surface sediments from Nam Co in Tibetan Plateau were collected and n-alkanes analysishad been conducted to identify the sources and spatial distribution of these molecular. The results indicated that n-alkanes rangingfrom 21 to 25 were identified to be derived from submerged plants, while n-alkanes ranging from 27 to 33 with n-C₂₉ or n-C₃₁peakwere derived from land plants except Androsace tapete and Sabina pingii. These two species contain n-alkanes with n-C₃₃ peak whichwere seldom reported before. Combined with information on plant sources and principal component analyses, three distinct groups ofn-alkanes with different spatial distribution in surface sediments were defined. Short-chain n-alkanes derived from photosyntheticbacteria and algae were relatively uniform in whole lake. But concentration of long chain n-alkanes gradually reduce from lake shoreto center coincided with transport distance increasing, indicating the main controlling mechanism of spatial distributions in surfacesediments was connected with biodegradation.