Dust particles were produced in situ using reactive mixtures (SiH4/C2H4/Ar) in radio-frequency(RF) discharge. To get more information about dusty plasma, Langmuir probe and optical emission spectroscopy diagnoses were introduced. Then the emission intensities of Si+ 390.6 nm, Si2+ 380.6 nm and C+ 426.7 nm as a function of pressure, RF power, and flow rates of SiH4/C2H4 were presented. The emission intensities of Si+, Si2+ and C+ are enhanced with the increase of gas pressure and RF power. But as the flow rates of SiH4/C2H4 increase, the emission intensities are weakened. By using Langmuir probe, the density of dust particles was calculated from electron density and ion density, and then variation of the dust particle density with RF power was derived, which is basically consistent with the trend of SiH4/C2H4 dissociation.