Methods of rapid determination of arsenic in water samples by using three kinds of portable spectrophotometer were optimized and the contrast research on these methods was carried out in this paper. By testing the performance indexes of different instrumental methods and determining the arsenic in actual water samples，the advantages of different portable spectrophotometers were compared. The research result would be able to provide a reference for choosing the suitable monitoring instruments used in sudden environmental pollution accident. The experimental results showed: the detection limit of ZZW Ⅱ portable spectrophotometer(0.2 mg/L) was higher than that of JH 916 portable spectrophotometer (0.008mg/L)and PORS 15 V portable spectrophotometer(0.009 mg/L), it meant that the PORS 15 V portable spectrophotometer and JH 916 portable spectrophotometer had higher sensitivity in monitoring sudden environmental pollution accident than ZZW Ⅱ portable spectrophotometer. The method precision of JH 916 portable spectrophotometer and ZZW Ⅱ portable spectrophotometer were similar and the RSDs(relative standard deviation) were all below 5.7% (n=6).The method precision of PORS 15 V portable spectrophotometer was not better than the other two spectrophotometers, the maximal RSD was 17%.The recoveries were 110%～126%(ZZW Ⅱ portable spectrophotometer),63%～108%(PORS 15 V portable spectrophotometer),78%～101%（JH 916 portable spectrophotometer）for the actual water samples.There was significant difference between the precision of standard method in lab and the precision of the three kinds of portable spectrophotometer,the maximal relative deviations were -19.0%（ZZW Ⅱ portable spectrophotometer），17.0%（PORS 15 V portable spectrophotometer），-15.0%（JH 916 portable spectroph otometer）.