Abstract: Based on the traditional and modern analyzed techniques，such as WinRHIZO root analysis system，dilution-plate method，PCR-DGGE etc.，the effect of low phosphorus stress on root growth，soil microbial properties and bacterial diversity under low phosphorus stress were analyzed. The results showed that the root length，surface area，volume and tip number were all decreased under low phosphorus stress. Additionally，soil microbial biomass，enzyme activities，microbial biomass（C，N，P）and soil bacterial diversity index（H），richness（S）and evenness index（Eh）were all also decreased under low phosphorus stress. However，some bacteria groups，such as Methyl bacterium（sp.），which have the function of soluble phosphorus，disappear in rhizosphere soil under low phosphorus stress condition. Moreover，it indicated that the degradation of soil fertility and soil bacterial community structure in rhizosphere were the main reason for the poor growth of tomatoes. The balance fertilization has an important function in improving the growth of tomatoes，soil fertility and health.

Key words: tomato, low phosphorus stress, root, soil bacterial diversity, PCR-DGGE