Konta, 25, was chasing the biggest title of her career but unravelled against the Polish number three seed after a battling first-set display.
The 11th seed, who has made the world top 10, fought back from 4-2 but could not make it 5-5 after missing a volley.
"I'm very pleased with this week, it was pretty spectacular," said Konta.
"I'm really enjoying my journey and looking forward to matches like this against players like Agnieszka," she added.
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Konta became the first British woman for 32 years to make the world top 10 after reaching the final. The last British woman to achieve that before her was Jo Durie in 1984.
Relive finals day at the China Open
In the men's final, Andy Murray secured his fifth singles title of 2016 - and 40th of his career - by beating Grigor Dimitrov 6-4 7-6 (7-2).
After dropping her serve twice in each set, Konta tried to even the scoreline in the second, pushing Radwanska to two break points in the sixth game.
However, Radwanska shot a forehand down the line to save her service game.
Konta held the next with a forehand drop shot, only for her opponent to then serve for the title, firing her only ace of the match.
BBC tennis correspondent Russell Fuller
Konta was well beaten in the end by the world number three, but will officially be a top-10 player on Monday morning and now has a very good chance of qualifying for the season-ending championships in Singapore.
Konta has moved into the eighth and final qualifying position, but has only a 10-point advantage over ninth-placed Slovak Dominika Cibulkova.
There are two qualifying weeks remaining, with Konta now heading to Hong Kong, where she has drawn fellow Britain Naomi Broady in the first round.
British number one Johanna Konta was overpowered 6-4 6-2 by world number three Agnieszka Radwanska in the final of the China Open.