The invention discloses a preparation method of 
cardanol triblock polyether, including: 1) washing a reaction kettle until clean with 
distilled water and 
drying the reaction kettle; 2) sucking 400-500parts of 
cardanol and 1-5 parts of an alkali catalyst into the reaction kettle; 3) pressing metered 
ethylene oxide, in liquid status, into the reaction kettle with 
nitrogen gas through an 
ethylene oxide feeder; 4) after the 
ethylene oxide is fed completely, pressing 200-680 parts of metered propylene 
epoxide, in liquid status, into the reaction kettle with 
nitrogen gas through a propylene epoxidefeeder, and performing a 
polymerization reaction; 5) after the reaction is completed, pressing 370-885 parts of metered 
ethylene oxide, in liquid status, into the reaction kettle with 
nitrogen gas through the 
ethylene oxide feeder, and performing a 
polymerization reaction; 6) degassing the product, reducing the temperature to about 70 DEG C, pressing the product into a homogenizing kettle, adding1.3-5.3 parts of glacial 
acetic acid for 
neutralization, and if qualified, delivering and packaging the product. The 
cardanol triblock polyether is biodegradable and environment-friendly, belongs tononionic surfactants, and has excellent cleaning capability and low-foaming property.