The objective of this study is to find out the key factors of well productivity in tight oil reservoir. According to the analysis of influence factors, eight factors are selected by taking the Chang 7 reservoir in Ordos basin for example. Gray correlative method is used to calculate the eight parameters correlation and check the influences on well productivity. The result shows that: sand volume, initial oil saturation, resistivity, interval transit time, porosity, perforation thickness, permeability and thickness effects on well production are smaller and smaller. The enrichment zones of Chang 7 reservoir are selected by using the results. Average well production in enrichment zones is 11.88m3/d, which is significantly higher than 6.43m3/d of the other regions. Gray correlative method is effective and convenient to analyze well productivity parameters in tight oil reservoirs.