i want to control a high voltage using 555 ic in monostable configuration
and the high voltage pulse should last until the output of the monostable will be high.
i am using the above circuit for timming.
I didn't hear a question. You are most likely needing a high voltage switch and possibly a level translation or isolated driver. But you didn't specify high voltage (100V, 1000V 10 kV?) intended current and additional circuit constraints.