In order to availably solve the crosstalk of the traditionally optically pumped magnetometer, in which an oscillating magnetic field drives transitions between Zeeman magneti c sublevels,an all-optical cesium (Cs) atomic magnetometer based on Bell-Bloom structure has been investigated and demonstrated experimentally in this paper.When there is an external magnetic fie ld,by analyzing the Larmor precession spectrum of the polarized ground state atoms induced by a modulated pump laser,the atomic magnetometer with high sensitivity is achieved.First,we pres ent the operating principle of the magnetometer with amplitude modulation and set up the experi mental system by means of a three-layer magnetic shield.Then in the case of 100nT field by opt imizing the experimental parameters,i.e.,the frequency and intensity of the pump laser,we have obtained the atomic precession spectrum with line width (full width at half maximum) of 22Hz and signal noise ratio (SNR) of 3.2×10^4per unit hertz band width,and then have evaluate d the magnetometer with an intrinsic sensitivity of 100fT/Hz1/2 and spatial resolution small er than 1.2cm,while the experimentally closed loop test shows that the cesium atomic magnetometer would have the sensitivity of 120fT/Hz1/2 and response time of 300ms.