When the partial discharge in SF₆ insulated equipment ceases or the concentration of decomposition products are sampled and delivered to laboratory examination, the concentration of decomposition products will decay with a certain degree over time in despite of the stationary equipment or sample.To improve the accuracy and reliability of the detection of decomposition products, the standing effect of the decomposition products decaying over time is studied.By analysis of the SF₆ decomposition mechanism, the SOF₂、SO₂F₂、CO₂ are considered typical components of the decomposition products.Model with floating potential defect is setup in a 90 L chamber suspension, and then a voltage twice larger than an initial partial discharge voltage is applied to the model to cause SF₆ to decompose.The varying tendency with time and initial content of the three concentrations of decomposed products and the concentration ratio are studied.The results show that contents of SOF₂ and SO₂F₂ decreases gradually over time, and the higher their initial content, the bigger the rate of decrease will be.On the contrary, the content of CO₂ remains steady.The level of SOF₂ falls more quickly than that of SO₂F₂.The ratio of two gas composition contents, φ(SOF₂)/φ(SO₂F₂), decreases with standing time at the initial 12 h, and then comes into stable state gradually after 24 h.