Laser induced fluorescence technique is a convienient, non-traumatic and high sensitive mehtod for tumor detection. The principle is that photosensitizers such as hematoporphyrin derivtives (HpD) has a special affinity to cancerous tissues. Being injected hematoporphyrin and excited with laser of a certain wavelength, cancerous tissues have characteristic fluorescentic peaks near 630 nm and 690 nm, while no such peaks have been observed in normal tissues. So it can be applied to tumor diagnosis. In this paper, we report small dosage of hematoporphyrin is applied to photosensitive diagnosis and the establishment of laser-induced fluorescence detection system with optical multichannel analysis (OMA) as it core. The LIF system is composed of three parts: 1 . fluorescence excitation and reception including laser machine as the exciting resource, exciting and recepting part and the corresponding light path coupling system. 2. photo-electricity transformation including OMA 4 system, electricity resource, cooling device, multi-color device with three gratings, and the multi-color device monitor. 3. computer signals handling including computer (Gateway 2000, 486 DX2/66). Control band connecting computer with OMA, printer, spectrum analysis and data transformation software. This paper introduced the system structure, regulaiton and operation methods in detail. Among them, the establishment of an excellent light path system, especially the good coupling between the exciting part (laser machine) and the recepting part (OMA) is the key to success .We have exprimented three kinds of fibers: coaxial fiber, parallel fiber and monofilament fiber. After comparing their advantages, disadvantages and working ways, we choose two pieces of paralled fibers (600nm) used to diagnosis of intralumatic tumors in clinic. Development of manofilament fiber is being carried out, too, The appropriate choice o flaser machine also has a great influuence to the exciting efeciency. Pratice has indicated that this system has high sensitivity and wide dynamic range. It is easy to operate the programme with menu can greatly improve the effeciency. With fiber, it can be applied to detect both superficial and intralumatic tumors. Complicated data handling also can be carried out with the advanced spectrum analysis programme. From our experimental and clinical reults, we believe this system has atained primary requirements on designment and clinic. In order to increase the sensitivity and reduce the sufferings of patients. Improvement of this system is necessary.