This paper investigates hospital bed planning problem in a single department, proposing a method combining Monte Carlo simulation and queuing theory to determine bed scale and allocation. Firstly, we establish a multi-type patient mixed queuing system and simulate it via Monte Carlo simulation, obtaining major performances of the queue. Then, bed scale is determined based on average waiting time of patients as well as bed utilization constraint. Furthermore, a mathematical model is constructed to minimize the total waiting time of all patients, thereby solving the bed allocation problem. Finally, the model is validated on MATLAB using ophthalmology department as an example. This study shows that Monte Carlo simulation is an efficient method for determining and controlling the scale of hospital beds when considering complexities, such as different arrival rates of patients and length of hospital stay distributions. This work provides hospital managers with an effective approach for hospital bed planning.