Fourteen government agencies, including the National Health and Family Planning Commission and the public security ministry, have been tasked to crack down on the illegal act.
China has the world's highest sex ratio at birth with 118 boys born for every 100 girls last year because of selective abortion under a strict birth control policy in a culture that prefers boys.
It is illegal in China, which has population of 1.3 billion to check the sex of an unborn child for non-medical reasons.
Hospitals and clinics were told to increase supervision of staff drawing blood from pregnant women and border control officials were ordered to step up checks to stop the movement of unauthorised blood samples.
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Whistle-blowers who report such services will be rewarded.
Illegal clinics in China with portable ultrasound scanners have been a popular choice with expectant parents, but in recent years, more have been sending blood samples mostly to Hong Kong for DNA tests.
In October last year, a Hong Kong woman was caught carrying 16 tubes of blood across the Lo Wu checkpoint.
For 4,000 yuan (USD 660), a pregnant Chinese woman could send a tube of her blood, wrapped in dry ice, to a Hong Kong blood test centre through Shenzhen.
The blood would be tested within 72 hours of being drawn and the results and a report would be available the next day, he said.
"We never run the risk of arranging to send a bulk consignment of tubes. We'd rather have more people cross the border more frequently and carry just two or three tubes each time," the agent said.