In the IRCS(integrated radar and communication system), which uses OFDM(orthogonal frequency division multiplexing) signals, the CP(cyclic prefix) and pilots can cause the problem of high peak to side lobe level in autocorrelation operation, which deteriorates the radar detection performance seriously. To solve this problem, a new RadCom signal based on TDS-OFDM(time domain synchronization OFDM) was proposed. The TDS-OFDM adopts TS(training sequence) for guard interval, as well as synchronization and channel estimation, so that the CP and pilots can be avoided. First, the ambiguity function of TDS-OFDM RadCom signal was analyzed. And then, TS was optimized to suppress the range side lobe of TDS-OFDM signal and maintain the autocorrelation properties of TS simultaneously. Theoretical derivation and simulation results show that TDS-OFDM signals are more suitable than CP-OFDM signals for IRCS.