Isolation Capacitance (Cio)
Actually i want to measure it in a practical way to verify the value
  in the datasheet. How and which equipment i should use to measure the
  isolation capacitance of digital isolator?


Use an oscilloscope with known input capacitance (that is quite a common thing to know for a decent oscilloscope) and place the device under test in series with the input to the o-scope and feed an input signal to isolated port of the device and compare the AC amplitudes of input and output and get a decent measure for the attenuation: - 



Use a frequency of around 1 MHz so that the scope's input capacitance dominates the input resistance (usually 1 Mohm or 10 Mohm).

Basically you are forming a potential divider and using input and output amplitudes to calculate the "unknown" device capacitance.