In a coherent direct sequence spread spectrum system with a spreading sequence whose period is one bit long, the performance of a delay locked loop is analyzed in the presence of CW interference and Additive Noise. The impact of CW interference on DLL should be a discrete sinusoid more than Gaussian noise which is traditionally recognized. the frequency, amplitude and phase of the discrete sinusoid are proposed. The baseband model of DLL in the presence of CW is also proposed. According to the model, the steady-state tracking error of the firstorder loop and the second-order loop is observed in the absence of noise. The Fokker-plank equation is utilized to analyze the steady-state tracking error probability distribution function (pdf) of the first-order loop in the presence of Gaussian noise. These expressions are then compared with computer simulations.