Taking tomato planted in plots in spring summer greenhouse as experiment material, the correlations between maximum daily shrinkage (MDS) in tomato stem diameter and meteorological factors such as water surface evaporation Ew , daily maximum temperature Tmax , daily average temperature Tm , daily average vapor pressure deficit DVPDm , midday vapor pressure deficit DVPDmd , daily total radiation Rs and daily maximum radiation Rmax were studied by using path analysis method. The results indicated that the direct path coefficients between Rmax ,DVPDm , Ew and MDS were all positive. The Rmax’s coefficient is the highest and the DVPDm’s coefficient is the second. The correlations between MDS and Rmax , DVPDmwere significant, but the correlation between MDS and Ew was not significant. Therefore, the Rmax and DVPDm were decision variables which controlled tomato stem diameter variation directly in greenhouse. In addition, the direct path coefficients between Tmax, Tm , DVPDmd ,Rs and MDS were all negative, but their sum coefficients between direct and indirect path coefficients were all positive. Tmax ,Tm , DVPDm ,Rs had indirect influence on tomato stem diameter variation through Rmax and DVPDm . Based on this conclusion, the simulating equation between MDS and Rmax , DVPDm was established which was significant through test, and the calculated values of MDS could reflect its observed values exactly. 