Fallon said Britain would announce at a NATO meeting with Ukraine on Thursday plans to double spending on the training to around six million pounds ($9.4 million).
"We are doubling up our training of Ukrainian forces. We've already trained around 650. By this autumn we will have trained nearly 1,000," he told reporters.
"We've already been training in battlefield medicine, infantry skills, logistics, in tactical intelligence," he said.
To those tasks will be added training in medical evacuation, operating in winter conditions and reconnaissance skills.
Britain now has 75 trainers working at six sites in western Ukraine and that number will increase "a little" under the expanded program, Fallon added.
"This is not designed to be escalatory or provocative. This is helping to save lives," Fallon said.
More than 6,200 people have been killed in eastern Ukraine since the conflict erupted there in April 2014 after the ousting of a Russian-backed president in Kiev amid street protests. Ukraine's new leaders want to move their former Soviet republic away from Moscow's orbit towards integration with Europe.
Fallon said Britain would also contribute to the cost of providing 200 secure communications devices to Ukraine's military.
The United States, Canada and Poland are also training or have announced plans to train the Ukrainian armed forces.
Some 200 Canadian troops will provide training in combat skills to Ukraine's National Guard from August or September, Canadian Defence Minister Jason Kenney told reporters at the NATO meeting.
The Canadians will also offer training for military police, aerial reconnaissance, medical evacuation and improvised bomb detection, Kenney said.