【Objective】 Composition and component ratio of soil humus are important indicators for assessing soil organic carbon quality, and also have important influences on soil structure and quality. Soil humus varies in combination form and hence in effect on soil structure and soil fertility as well. Therefore, it is of great significance to rational fertilization in facilitated vegetable production to study effect of application of nitrogen(N) fertilizer and organic manure on component contents, composition and profile distribution of soil humus under greenhouse. 【Method】For this study a field fertilization experiment was conducted in a greenhouse growing tomato for five consecutive years. The experiment was designed to have four treatments (N0, N1, N2 and N3) of applying merely N fertilizer at a rate of 0, 187.5, 375.0, and 562.5 kg·hm^-2, respectively, and four (MN0, MN1, MN2 and MN3) combined application of N fertilizer and organic manure that is, each of the four N treatments coupled with organic manure (M: 75 000 kg·hm^-2). Total organic carbon (TOC), water soluble organic carbon (WSOC), soil loosely and stably combined humic acid carbon (HA-C) and fulvic acid carbon (FA-C) in all the eight treatments were monitored for content, composition and profile distribution in the greenhouse soil. Soil water soluble substance (WSS), loosely combined humus and stably combined humus were extracted with Fu Jiping, soil humic acid (HA) and fulvic acid (FA) separated with the modified humus component method, and organic carbon content of each determined. 【Result】 In all fertilization treatments, the contents of TOC, WSOC, stably combined humic acid carbon (HA₂-C) and fulvic acid carbon (FA₂-C) gradually decreased with soil depth, whereas the contents of loosely combined humic acid carbon (HA₁-C) and fulvic acid carbon (FA₁-C) increased first and then decreased with soil depth. But the contents of soil TOC, WSOC and humus components were the highest in the 0~20 cm soil layer. Compared with application of mere N fertilizer, combined fertilization increased the content of TOC, WSOC, HA1-C, FA₁-C and HA₂-C by 12.44%~87.38%, 11.01%~168.32%, 10.15%~235.54%, 2.41%~205.21% and 3.42%~92.61%, respectively, in the 0~50 cm soil layer. The effect was especially significant for TOC, WSOC, HA₁-C, FA₁-C and HA₂-C in the 0~20 cm soil layer (P< 0.05) and for HA₁-C, FA₁-C and HA₂-C in the 40~50 cm soil layer (P< 0.05). Combined fertilization also significantly improved the ratio of HA₁/FA₁, HA₂/FA₂, and HA/FA and PQ₁ (HA₁-C/(HA₁-C+ FA₁-C)), PQ₂ (HA₂-C/(HA₂-C+ FA₂-C)), and PQ (HA-C/(HA-C+ FA-C)) in the 0~20 cm soil layer (P< 0.05), increased the C/N ratios of HA1, HA₂ and FA₁, but slightly decreased that of FA₂ in the 0~20 cm soil layer. Besides, combined fertilization also decreased E₄/E₆ (The ratio of absorbance at 465 nm and 665 nm wavelengths) of the soil HA, but increased E₄/E₆ of the soil FA.【Conclusion】 Under the conditions of tomato cultivation in the greenhouse, combined fertilization for 5 consecutive years not only significantly increases the amount of soil organic carbon in the 0~20 cm soil layer, but also helps FA transform to HA, promotes formation and accumulation of humic acid, especially loosely combined humic acid, and consequently improves quality of the soil organic carbon significantly. It is, therefore, concluded that combined application of 187.5 kg·hm^-2 N fertilizer and 75 000 kg·hm^-2 organic manure is the best option to improve quantity and quality of soil organic carbon.