The invention relates to a method for detecting sand production rate in the process of thick oil exploitation in an oil field and a device thereof. A set of diluter refiller is arranged on an oil pipeline. The concentration of original thick oil is diluted to less than 100mPa.S. The outer wall of a downstream curved conduit of the oil pipeline connected with the diluter refiller is wound with an ultrasonic sensor. The positive pole and the negative pole of the ultrasonic sensor respectively extract a positive electrode terminal and a negative electrode terminal which are connected to the signal input end of a sand production rate detecting circuit. The negative electrode terminal is grounded. The volume flow Q2 of sand in the pipeline is calculated through measuring the refilling flow Q4 of the diluter and the total flow Q1 of the diluter which flows the ultrasonic sensor after diluted, and through the voltage change which is caused by that solidoid sand collides the pipe wall and measured by the ultrasonic sensor. Thereby, the percentage composition of the volume flow of the sand in the original thick oil is obtained. The invention effectively solves the sand production rate detecting problem of thick oil by using the diluter refiller and the ultrasonic sensor. The detecting method and the device are effective.