Although the spectrophotometer for biochemical analyzer (BCA) has been applied to the properties analysis of biological samples including blood, some factors result in reducing the spectral measurement accuracy in practice. For example, the spectral absorbances are different for the various components in sample at different absorption wavebands, especially at the larger energy attentuation waveband and noncharacteristic absorption waveband, which leads to the signals of strong absorbances are very large, but for weak absorbances, the singals are very small even covered by noises. Additionally, various noises generated by electronic devices and straylight also bring serious interference for system. To solve these drawbacks above mentioned, an optimize algorithm of automatic adjustment of linear charge coupled devices(CCD) integration time combined with time and data division was used to realize the separate exposure for strong absorption and weak absorption spectrum, which improved the weak signals under the condition of strong signals were normal. Experiments were done by using a custombulit high resolution spectrophotometer for BCA based on CzernyTurner splittinglight monochrometer and linear CCD. Experimental results demonstrated that the improved method effectively enhanced the spectral measurement accuracy, system performance and signaltonoise ratio. In additon, the spectral range of this spectrophotometer for BCA can reache 300~800 nm, wavelength resolution less than 2 nm.