One of the important protection characteristics in online distributed generation is to identify the islanding operation. And in accordance with standards of Distribution network in power system, this identification must take in less Than 2 seconds. There are several Methods in Micro grids islanding detection. Islanding detection technique may generally be divided into remote and local techniques. In remote, The detection algorithm is on the grid side, in local the detection is on the DG side. Local Techniques consisting of active and passive and hybrid methods. Passive methods have been studied in This paper. The most commonly used passive islanding detection techniques are presented in This paper. This paper aims to compare these methods with their non-Detection zone and speed of detection. The comparison can help researchers determine the best method for their product.