A villager in Sichuan province was diagnosed with falciparum malaria, the most dangerous type of the disease, in May and 143 people who had contact with the patient took preventative medicine, the official Xinhua news agency said.
They soon started complaining of exhaustion and nausea, and a child who suffered a headache after taking the drugs died earlier this week, the report late Wednesday quoted the provincial health department as saying.
A statement on the department's website confirmed the death, adding that one other person was in a serious condition in hospital but that 103 others were out of danger.
Health authorities were investigating why the drugs caused such a reaction.
China is regularly plagued by food and medicine-related product safety concerns.
In May, authorities fined two drug companies, including one authorised to make swine flu vaccines, for producing substandard rabies shots.
And allegations in March that four children had died and more than 70 others fell ill in the northern province of Shanxi after they received vaccines against illnesses such as hepatitis B and rabies caused huge concern.