The present invention provides pharmaceutical composition of muscarinic antagonist in oral solution dosage form. The oral solution composition comprises of muscarinic antagonist with other pharmaceutical excipients such as vehicle, preservative, buffering agent, sweetener and flavouring agent. The present invention is an oral solution of muscarinic antagonist that is free from allergic preservatives and having improved stability without risk of over dosage of the drug. The present invention also provides oral solution with flavor that has masked bitter taste of muscarinic antagonist. Further, the present invention also provides a process for preparation thereof.