According to the field data, there are several methods to reduce the drilling cost of future wells. One of these methods is the optimization of drilling parameters to obtain the maximum rate of penetration (ROP) in each bit run. Many parameters affect ROP like hole cleaning (including drillstring rotation speed (N), weight on bit (WOB), floundering phenomena, mud rheology), tooth wear, formation hardness (including depth and kind of formation), differential pressure (including mud weight (MW)), etc. Considering the geology and rock mechanical parameters, each part of well has different recommended parameters from the other parts. To optimize the drilling parameters, it is required that an appropriate ROP model to be selected until acceptable results are obtained. In literature, there are various applicable models to predict the ROP such as Bourgoyne and Young model, Bingham model and modified Warren model. It is desired to calculate and predict the proper model of ROP for roller-cone and PDC bits in each well by using the mentioned models and then verify the validity of each model by comparing with field data. Analyzing the drilling parameters by computer optimizationyields recommended range of parameters for each bit. The applications of present study are predicting the proper penetration rate, optimizing the drilling parameters, estimating the drilling time of well and eventually reducing the drilling cost for future wells.