To study effects of intercropping tomato with leguminous crops on growth of tomato, a field experiment was carried out in the suburbs of Shanghai, East China. The experiment was designed to have four treatments: (I) monocropping tomato, as control; (II) intercropping tomato and kidney bean (Phaseolus vulgaris L.); (III) intercropping tomato and Phaseolus vulgaris L. var. humilis Alef. (IV) intercropping tomato and amaranth (Amaranthus mangostanus L.). Rape cake manure was applied to each plot as base fertilizer at a rate of 1.0 kg m ^-2. No sidedressing of fertilizers, pesticides or herbicides were applied during the whole experiment to exclude their disturbances to tomato growth, soil nutrients and enzyme activities.It was found that intercropping tomato with legume could significantly increase plant height of tomato. Compared with control (Treatment I), Treatments II and III increased plant height of the tomato by 10.0% and 10.1%, respectively; and Treatment II increased tomato yield by 15.7%. The two treatments also significantly increased soil nutrients. Compared with control, Treatment II increases total N in the soil by 16.9%; alkali-hydrolyzable N by 14.0%; available P by 26.6% and available K by 23.4%. Likewise, Treatment III increased alkali-hydrolyzable N and available P by 8.0% and 22.9%, respectively. Besides, the treatments significantly increased soil enzyme activities. Compared with control, Treatment II increased the activities of urease, sucrase and phosphatase by 64.6%, 26.8% and 25.5%, respectively. Likewise, Treatment III increased the activities of sucrase and phosphatase by 17.2% and 15.1%, respectively. In contrast, intercropping with non-leguminous crop, Treatment IV, had no obvious effects on plant height, reduced yield of the tomato by 11.1%. It did not have any positive effects on soil nutrients, except for soil available K. However, it improved the activities of sucrase and phosphatase by 17.4% and 7.5%, respectively. In Treatments II and III, nitrogen fixation by leguminous crops and dense root system of the intercropping system that decomposes soil minerals improved soil fertility significantly, which is the main reason for the increase in tomato yield. In Treatment IV, the non-leguminous crop, amaranth, does not have any capability of fixing nitrogen. So Treatment IV reduced yield of the yield as a result of their competition for N and P nutrients. In Treatment II and III the activity of soil urease was significantly enhanced as the treatments increased soil N. The activities of sucrase and phosphatase were significantly enhanced in all the intercropping treatments possibly because intercropping had denser roots.Urease activity was significantly correlated with the contents of total N, alkali-hydrolyzable N, available P and available K in all the plot soils (p<0.05). Especially, the correlation coefficient between the urease activity and alkali-hydrolyzable N reached 0.928 (p<0.01). The activity of sucrase was significantly correlated with the contents of total N, alkali-hydrolyzable N, organic matter, total P, available P and available K（p<0.05）in the soils; and that of phosphatase significantly with total N, alkali-hydrolyzable N, available P and available K（p<0.01）. This fully suggests that there is a close relationship between enzyme activities and nutrient contents in the soils. Intercropping tomato with leguminous crops can not only raise soil fertility, but also increase tomato yield, thus making it feasible to reduce the use of fertilizer. Especially, intercropping of tomato with kidney bean can not only increase yield of the crop, but also make full use of space and raise land use efficiency, as the stems of kidney bean grow upward and wind around tomato plants. This, therefore, is a promising cultivation mode for tomato.