A method of producing a hollow laser beam (HLB) by directing the laser beam at a certain angle into a liquid core optical fiber (LCOF) is presented. The dependences of dark spot size DSS and beam width of the HLB on the propagation distance, and the length and core diameter of the LCOF are theoretically analyzed by modeling the generation system using Zemax. Using CS2 as core-liquid material, a part of theoretical result is experimentally demonstrated with 630 nm semiconductor laser. The results show that HLBs with adjustable DSS are obtained by changing the incident angle of the laser beam. DSS and beam width of the HLB are independent of the LCOF length, while related to its core diameter. This method has advantages of convenient operation, low cost and wide adjustable range of DSS. It can satisfy the needs of different applications.