Objective To evaluate the value of bronchoalveolar lavage fluid (BALF) detected by Mycobacterium tuberculosis (MTB) loop-mediated isothermal amplification (TB-LAMP) technique in the diagnosis of smear and culture negative pulmonary tuberculosis (PTB). Methods Clinical data of 254 patients who were clinically diagnosed with smear and culture negative PTB (3 times of both negative sputum smear and negative sputum culture) in a hospital from December 2017 to November 2018 were collected, all patients underwent bronchoscopy for taking bronchoscope brush or BALF specimens, they were divided into LAMP group (performing acid-fast staining smear, Lowenstein-Jensen culture, and TB-LAMP detection) and GeneXpert group (performing acid-fast staining smear, Lowenstein-Jensen culture, and GeneXpert MTB/RIF detection). Results 96 patients and 158 patients with smear and culture negative PTB were included in LAMP group and GeneXpert group respectively, there were no significant differences in gender and age between two groups of patients (both P>0.05). Positive rates of acid-fast staining, Lowenstein-Jensen culture, and TB-LAMP in LAMP group were 4.17%(n=4), 18.75%(n=18), and 52.08%(n=50)respectively;positive rates of acid-fast staining, Lowenstein-Jensen culture, and GeneXpert MTB/RIF in GeneXpert group were 3.80%(n=6), 12.66%(n=20), and 54.43%(n=86)respectively. Positive rates of TB-LAMP and GeneXpert MTB/RIF were both significantly different from acid-fast staining and Lowenstein-Jensen culture(both P<0.05). Positive rates of MTB detected by TB-LAMP and GeneXpert MTB/RIF was not significantly different. Conclusion Application of TB-LAMP for BALF has a good diagnostic efficacy on smear and culture negative PTB, it is fast, simple, accurate and economical, and is worth of promotion in clinical application.