Based on the theory of interaction between polarized light beam and birefringence crystal particles,relationship of the rotation frequency with the liquid viscosity coefficient was studied in the optical tweezers,simulations with Matlab were also made.It came to the conclusion that the rotation frequency of particles is affected by the liquid viscosity coefficient.The liquid viscosity depends on the temperature of liquid.So the change of the temperature can be obtained by observing the rotation frequency for the real-time temperature measurement.