Abstract: A pneumatic servovalve with even underlaps or uneven underlaps and its characteristics of control orifices were discussed. The pressure of the steadystate working point at x=0 is as much as 80% of the supply pressure for a servovalve with symmetric and even underlaps of the spool valve. But it is less than 80% of the supply pressure for a servovalve with symmetric but uneven underlaps where the underlaps of upstream is less than that of downstream. And it is larger than 80% of the supply pressure for a servovalve with symmetric but uneven underlaps where the underlaps of upstream is larger than that of downstream. Either a pneumatic servovalve with symmetric and even underlaps, or a pneumatic servovalve with symmetric and uneven underlaps has maximal leakage flow rate on neutral position of the spool valve. The theoretical results are in good agreement with the experimental results.