A new method for detecting circle with defects and noise using parametric deformable template is proposed. An energy function of the deformable template is defined according to geometric characteristics of the circle and gradient information of the image. The template then interacts dynamically with the image and energy function by altering its parameter values to maximize the energy function. The final parameter values (maximum) can give the location of the circle according to definition of the energy function. In order to raise the matching speed, a decreased search region is given by estimating values of the radius and the center of the circle. Then the energy function is optimized using greedy method in the search region. Experimental results show that the algorithm can localize the circle within a pixel and about 0.5 s; even the circle has defects and noise. This method has good resistence to interference and noise, and fast operation.