The invention provides a carbocisteine oral solution and a preparation method thereof, relating to the technical field of medicine, comprising carbocisteine, glycerin, lemon juice, loquat, antioxidant, solution stabilizer, flavoring agent, and pH regulator; The method comprises the following steps: (1) taking the glycerin, lemon juice and loquat dew of the formula quantity, adding ultrapure water, and ultrasonic treatment for 10-12min; (2) adding the carbocisteine of the formula quantity into the solution in step (1) , heated to boiling, then stirred, and mixed evenly; (3) adding antioxidant, solution stabilizer, flavoring agent in boiling state, keeping boiling for 5‑8min, standing, and cooling to room temperature; (4) adding pH adjustment medicament, stir evenly, make the pH value of solution be 6.5-7.0, make carbocisteine oral solution. The method of the invention has simple process and low cost, and the obtained carbocisteine oral solution has good water solubility and is easy to industrialized production, and solves the problems of carbocisteine taste discomfort and low bioavailability.