The invention, which relates to the video coding 
processing field, discloses a method for calculating a 
coding distortion degree and a coding 
mode control and a 
system thereof. According to the invention, the method comprises: a predicted pixel value of a coding 
macro block in a current coding mode is obtained and a predicted 
residual value is calculated based on the predicted pixel value and the coding 
macro block pixel value; the predicted 
residual value is processed by quantization and 
inverse quantization during a coding process in a current coding mode to obtain a predicted 
residual value with quantization losses; and a difference spare quadratic sum of the predicted residual value and the predicted residual value with quantization losses is used as a 
coding distortion degree in the current coding mode. According to the invention, because the difference spare quadratic sum of the predicted residual value and the predicted residual value with quantization losses is used as the 
coding distortion degree, the time 
delay of a prediction module, a 
prediction residual calculation module, and a rebuilding module in a calculation passage is avoided; and a problem that a serious data passage 
delay phenomenon occurs when the 
distortion degree is calculated based on the traditional SSD coding module control strategy can be solved.