The Xinjiang Uyghur Autonomous Region is the main processing tomato production area of China. So production of processing tomatoes is the backbone of the local economy. To meet the demand for processing tomatoes of the market, continuous cropping or monocropping is widely adopted for the production of processing tomatoes, but unfortunately it has become the main factor limiting stable production and high yield of the crop in the region. It is, therefore, important to understand the mechanism of continuous tomato cropping regulating soil microbial activity. The objective of this study was to explore effects of continuous tomato cropping on physical, chemical and biological properties of the soil, in a view to providing a theoretical basis for sustainable development of the processing tomato industry in Xinjiang. A mono-cropping field experiment started in 2007 at the experiment station of the Agriculture College, Shihezi University. The cultivar of processing tomato used in the experiment was “Ligeer 87-5”. Soil samples were collected for analysis from plots different in cultivation history, 3, 5, and 7 yr of continuous cropping and from the control plot which had been undergoing fallow for 3 years before tomato was planted in 2014. Results show that with continuous cropping going on soil pH increased and soil total P, available P and total K increased first and then decreased; soil bulk density did not change much. After 7 years of continuous cropping, soil organic matter content, total N, and readily available K decreased by 8, 21 and 29%, respectively. Moreover, soil microbial biomass C (SMBC), soil microbial biomass N (SMBN), and the microbial quotient (qMB) all displayed declining trends as continuous cropping went on and decreased by 52, 79, and 48%, respectively, after 7 years of continuous cropping. Soil microbial biomass P (SMBP) increased during the first three years of continuous cropping, peaking up to 1.6 times as high as that in the control and then decreased. Continuous cropping significantly increased the activity of soil catalase, but reduced the activities of urease, sucrase, polyphenoloxidase, and phosphatase. And what is more important, it led to a significant drop, as much as 34%, in yield of processing tomato, (p<0.01) in the treatment of 7 years as against the control. Correlation analysis shows significant correlations between soil pH, soil microbial biomass, qMB, soil enzyme activity and soil nutrient content. All the findings indicate that variations of soil microbial biomass and microbial activity may reflect changes in soil quality and thus can be used as biological indicators in evaluating soil fertility. Continuous cropping of processing tomato significantly increases soil pH and electrical conductivity and inhibites the activity of soil microbes, thus lowering soil fertility, and eventually yield of the crop. So the negative effects of continuous cropping are obvious. To maintain soil fertility and improve processing tomato production, it is essential to rotate processing tomato with cereal crops. In regions where farmland is limited in area, it is advisable to cultivate the crop continuously no more than three years.