Abstract: Taking Brassica napus L., an oil crop broadly cultivated in the world as test object, a greenhouse experiment was conducted to study the effects of oligochitosan on the leaf super oxide dismutase (SOD) and peroxidase (POD) activities, proline content, chlorophyll fluorescence parameters, and relative water content under drought stress. After spraying oligochitosan, the leaf SOD and POD activities decreased at early stage but increased obviously at late stage, whereas the leaf proline content increased obviously throughout the process. The maximum quantum yield of photosystem II (F_v/F_m), excitation capture efficiency of open centers (F_v′/F_m′), photochemical quenching coefficient (q_P), and effective quantum yield of photosystem II photochemistry (Φ_PSII) all increased obviously, while the minimal fluorescence of darkadapted state (F_o) and nonphotochemical quenching coefficient (q_N) had an obvious decrease. The leaf relative water content also increased. It was suggested that oligochitosan could improve the related physiological indices of B. napus against drought, and further, enhance the drought resistance of the oil crop.