The incident happened in northwestern Xinjiang Uygur autonomous region has gone viral online, prompting Apple Inc, makers of iPhone, to launch a "thorough probe" into the case.
The older sister of victim Ma Ailun said on Sina Weibo, the Chinese equivalent of Twitter, that Ma was electrocuted while trying to answer a call on her iPhone when the device was charging.
"(I) hope that Apple Inc can give us an explanation. I also hope that all of you will refrain from using your mobile devices while charging," state-run China Daily quoted her as saying in the Weibo post.
Ma's father, Ma Guanghui, confirmed that his daughter was electrocuted and her body showed signs of electrocution, the report said.
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Ma was previously employed as a flight attendant at China Southern Airlines, although she recently quit her job.
Local police also confirmed that Ma did die of electrocution, but they have yet to verify if her phone was involved in the incident.
Ma's sister said she hopes to seek justice from Apple.
Apple, in a statement, said the company felt "deeply sorry for the unfortunate accident" and expressed condolence to the victim and her family.