【Objective】 Since the 1980s, a large area of meadow on the Qinghai-Tibet Plateau has been reclaimed to be cropland along with a long term of fertilization, which may have an import influence on soil humus and thereby soil fertility and environmental chemical process in soil. This study was oriented to explore effects of reclamation and long-term fertilization on humification degree, relative molecular weight, aromaticity and source of the humus in an oilseed cole field of chernozem in Qinghai, with a view of providing certain theoretical support for management of agricultural activities in meadows of the QingHai-Tibet Plateau. 【Method】 In this study, basic physic-chemical properties of chernozem and spectral properties of the humus in a cole field of chernozem under reclamation and long-term fertilization and a tract of virgin meadow of chernozem in Qinghai were characterized by means of UV-vis, Fourier-transform infrared and Parallel factor analysis, three-dimensional fluorescence spectroscopy for comparison.【Result】 Results show that reclamation and long-term fertilization significantly affected basic physico-chemical properties of the chernozem, the spectral properties of the humic acid and fulvic acid in the soil and molecular composition of the soil humic substances. In terms of soil physico-chemical properties, reclamation significantly reduced soil organic matter, while fertilization enhanced soil fertility and nutrient supply. However, long-term fertilization led to soil acidification, while slowing down the decreasing process of soil organic matter, thus causing degradation of soil quality. UV-vis spectra indicate that reclamation and long-term fertilization enhanced humification degree, relative molecular weight, aromaticity and dependence-on-extraneous-sources of humic acids, but affected all the indices of fulvic acids reversely, except for dependence-on-extraneous-sources, while FT-IR spectra indicate that long-term fertilization facilitated formation of carboxylic acids in the soil, increased biomass of the crops, which in turn depleted much carbohydrate and aliphatic organic matter in the soil. Parallel factor analysis and three-dimensional fluorescence spectra identified five components of soil humus including two types of humic acid-like substances, two types of fulvic acid-like substances and a soluble microbial by-product. Reclamation and long-term fertilization also affected composition of the humus, by relatively expanding the fraction of large-molecule humic acids and shrinking the fraction of small ones, but expanded the fractions of both large- and small-molecular fulvic acids, especially the latter. 【Conclusion】All the findings in this study suggest that careful attention should be paid to agricultural reclamation of the meadow resources of the Qinghai-Tibet Plateau and that it is advisable to apply organic manure to retard reduction of organic matter, and to expand the sources of fulvic acids while increasing humidification degree of soil humus. Further study on the response of functional structure of soil humus to the reclamation and long term of fertilization is also suggested to detect the carbon sequestration and to put forward management practice to maintain carbon balance in soil of the Qinghai-Tibet Plateau.