World number 22 Praneeth initially faced stiff resistance from the former Chinese world number one and Rio Olympic gold medallist before prevailing 21-18 21-13 in the semifinal clash.
While the first game was tight, the Indian shuttler completely dominated the second, ending the match in 46 minutes.
It was Praneeth's first win over Long in three attempts. he had lost to him at the Indonesian Master early this year and at Asian Championship last year in April.
Praneeth will now fight it out with top seed Chinese Shi Yuki in the final, which will be his first since the Thailand Open victory in June 2017.
P Kashyap, Ajay Jayaram, Sameer Verma and Shubankar Dey also featured in the men's singles but none could go beyond the second round.