In this article, using the retarding grid energy analyzer, we have measured the ion energy distributions in a low temperature radio fruquency plasma under the condition of different magnetic mirror parameters. At the centre of discharge cell, the ion energy distributions displace in the direction of low energy with the increase of the magnetic density without evident variation in the ion energy distribution width. With the increase of the magnetic mirror ratio, the ion energy distribution displaces in the direction of high energy, and the width of ion energy distribution became wider. So the magnetic mirror parameters have significant effect on the ion energy distributions.