The frequency and intensity noise of the probe laser in the integrating sphere cold atom clock (ISCAC) are studied theoretically and experimentally. The power spectral density of the relative intensity noise of the probe laser in the high frequency region (0.1-10 kHz) is maximally compressed by 15 dB with the methods of stabilization of laser power and the removal of stray light, and simultaneously the influence of the probe laser frequency noise on the ISCAC frequency stability is decreased to 9τ－1/2×10－15 where τ is the integration time.The theoretical analysis results show that, up to now, the influence of the probe laser frequency noise on the ISCAC frequency stability is 2.5τ－1/2×10－13. Thus a scheme to reduce the influence of the probe laser frequency noise is proposed, that is, the detection time is increased appropriately in a certain clock cycle. With this method, the influence of the probe laser frequency noise on the ISCAC frequency stability can be reduced to 9.4τ－1/2×10－14.