A method of precise first-path detection in CDMA mobile communications systems, comprising the steps of: a. calculating the noise threshold for the first-path detection according to the multi-path profile; b. judging whether there is a maximum point exceeding the noise threshold in the multi-path profile, if yes, carrying out side-lobe suppression at the maximum point which exceeds the noise threshold and obtaining candidate first path; otherwise, deciding that no first path exists, and exiting the entire process of first-path detection; c. judging according to the location of the candidate first path whether the first path is ambiguous, if yes, carrying out correction of first-path ambiguity, and outputting the corrected location of final first path; otherwise, outputting the location of candidate first path as the location of final first path; wherein the said side-lobe suppression in step b comprise: b1. from the starting location of the multi-path profile to the end of the multi-path profile, searching the location of the first maximum point exceeding the noise threshold of the profile thereof; b2. finding the location of the largest power value within N chips after the location of the current maximum point; b3. judging whether the largest power value in step b2 is larger than the power value at the location of the current maximum point by M dB or more, if yes, going to step b4; otherwise going to step b5; b4. from the next sampling point after the location of the current maximum point, searching in the multi-path profile the location of the first maximum point exceeding the noise threshold and taking this location as the location of the current maximum point, and then returning to step b2; b5. making the location of the current maximum point as the location of the candidate first path; where the feasible range of value of N is from 3:5 to 4.0, and the feasible range of value of a. calculating the noise threshold for the first-path detection according to the multi-path profile; b. judging whether there is a maximum point exceeding the noise threshold in the multi-path profile, if yes, carrying out side-lobe suppression at the maximum point which exceeds the noise threshold and obtaining candidate first path; otherwise, deciding that no first path exists, and exiting the entire process of first-path detection; c. judging according to the location of the candidate first path whether the first path is ambiguous, if yes, carrying out correction of first-path ambiguity, and outputting the corrected location of final first path; otherwise, outputting the location of candidate first path as the location of final first path; b1. from the starting location of the multi-path profile to the end of the multi-path profile, searching the location of the first maximum point exceeding the noise threshold of the profile thereof; b2. finding the location of the largest power value within N chips after the location of the current maximum point; b3. judging whether the largest power value in step b2 is larger than the power value at the location of the current maximum point by M dB or more, if yes, going to step b4; otherwise going to step b5; b4. from the next sampling point after the location of the current maximum point, searching in the multi-path profile the location of the first maximum point exceeding the noise threshold and taking this location as the location of the current maximum point, and then returning to step b2; b5. making the location of the current maximum point as the location of the candidate first path;