Some residue levels were hundreds of times higher than European Union food safety standards, according to tests carried out for a Greenpeace report "Chinese herbs: elixir of health or pesticides cocktail?", the latest to focus on the harmful effects of China's large-scale farming industry.
"These test results expose the cracks in the current industrial agriculture system that is heavily reliant on toxic chemicals at the expense of human and environmental health," said Greenpeace ecological farming campaigner Jing Wang.
"Chinese herbs are trusted and used as food ingredients for healing purposes by millions of people around the world. They are an iconic part of our heritage we must preserve. Chinese herbs should heal, not harm people and must be pesticide free."
Exposure to pesticide residue causes toxic chemicals to accumulate inside the body, leading to learning difficulties, hormone disruption and reproductive abnormalities, according to Greenpeace.
The group sampled 65 herb products, finding 51 different types of pesticide residues. Twenty-six of the samples contained pesticides that are illegal in China.
Some pesticides were found in "extremely high concentration", with residues on the san qi flower 500 times over safety limits and on the honeysuckle more than 100 times over.
The report follows an investigation by Greenpeace in April which revealed mountains of hazardous waste left from China's huge phosphate fertiliser industry are polluting nearby communities and waters.
China, the world's top maker of phosphate fertiliser, has seen production more than double over the past decade to 20 million tons last year, leaving 300 million tons of a byproduct called phosphogypsum that can contain harmful substances.
China's agricultural sector has expanded rapidly in recent years, and "intense" farming methods have been blamed by state media for recent food scares, including a deadly outbreak of bird flu earlier this year.