Longtime market bull Jeremy Siegel says the two-month market rally has been fueled by investors buying on the hope of tax reform and that is nearing its end.

"I'm very positive on the tax plan but it's buy on the anticipation, sell on the news," he said Tuesday on CNBC's "Closing Bell." "All the good things about the corporate tax plan have been built into the rally we have seen for the last two months and I'm not sure how much else there is really going to be."