To study the effect of Sauter diameter(D₃₂) of droplets on the explosion parameters, the effect of the droplets size of n-heptane (C₇H₁₆) on the explosion parameters in explosion vessel was numerically simulated, while controlling the total concentration of droplets of 80 g·m^-3, when changing the droplet size. Results show that when D₃₂ of n-heptane droplets is between 0-18.1 μm, the maximum explosion pressure p_max decreases gradually with the increase of D₃₂, the maximum value is 1.01 MPa and the minimum value is 0.9015 MPa. The maximum explosion pressure rise rate reveals an overall downward trend with the increase of D₃₂, which reaches the maximum value of 0.37571 MPa·ms^-1 at 0 μm, and the minimum value of 0.18439 MPa·ms^-1 at 18.1 μm. But in the range of 6.81-12 μm, the reverse mutation occurs, reaching the maximum value of 0.34217 MPa·ms^-1 at 10.1 μm, and then restoring the downward trend. The radial flame propagation velocity of droplets suddenly increases near the radial distance of 15 cm, and then decreases sharply after 16 cm. The maximum flame velocity varies with D₃₂ of droplets. Under the conditions of D₃₂=10.1, 12.9, 18.1, 6.81 μm and 0 μm, the maximum flame velocity of droplets field decreases successively. The maximum value is 5.714 m·s^-1, followed by 1.737, 1.36, 1.34 m·s^-1 and 1.27 m·s^-1.