A new calculation method is developed because of the existing problems in the current tilt angle measurement for automobile engine belt tensioner.The new coordinate systems are set up based on tensioner design,the plane direction of pulley is calculated through vector operations,and a new test program is written to process the data in order to get the tilt angle variation of tensioner within the whole working range.Application in huge amounts of test data proved the correctness and validity of the new test program,and the problems in the original method are solved.After the optimization,parameter settings are completely identical with product drawings,the tilt angle definition fits both mathematical rules and common engineering application better,measurement data from various types of tensioners can be processed without further modification,command lines are more compact and running efficiency becomes higher.The test results after this improvement provide more valuable references to the evaluation procedure of belt tensioner products.