In this paper, we find the reliability R of a component when it is exposed to four independent stresses and it having one strength for Lomax distribution. the reliability R was estimated by using four different estimations (MLE, RgE, LSE, and WLSE) methods. A comparison was made between the results of estimating the reliability function by MSE and MAPE criteria, that will get from a Monte Carlo simulation study. We found that the performance of ML is the best to.