The 25-year-old Liverpool fighter beat American Jackie Galloway 14-4 at +73kg, taking the top step on the podium after Olympic bronze in Rio last August.
She said: "I was devastated after Rio. And it's still a goal I need to get in Tokyo. I took off my gold medal (from 2015) and treated this as though it was double or quits. And I came back with double. I am just so happy."
Mahama Cho secured at least a bronze medal in the men's heavyweight class by advancing to the +87kg semi-finals, but there was disappointment for Lutalo Muhammad.
The 2016 Olympic silver medallist, who is on his comeback from knee surgery, was beaten 21-6 by Smaiyl Duisebay of Kazakhstan in the round of 32 in the under-87kg category.
Britain will be seeking further success when double Olympic champion Jade Jones competes on Thursday, but Wednesday belonged to Walkden.
She beat South Korea's Asian champion An Sae-bom before facing Galloway, who had defeated China's Zheng Shuyin, the Olympic over-67kg gold medallist in Brazil, in the semi-final.
She can secure a hat-trick of titles when the World Championships take place in Manchester in 2019.
Cho beat Iran's Sajjad Mardani 14-1 to advance to the last four.The Stockwell fighter, who lost the bronze-medal contest at the Rio Olympics, grew in confidence as he progressed to face Roman Kuznetsov of Russia.
Jade Slavin, meanwhile, missed out on a place in the under-73kg quarter-finals when she went down on golden point to Maria Espinoza, the 2008 Olympic champion and silver medallist in Brazil last summer.
Doncaster's Bradly Sinden joins Jones in action on Thursday, contesting the men's under-63kg.
