This paper presents CCD multicolor photometry for 304 old star clusters in the nearby spiral galaxy M31 .
Of which photometry of 55 star clusters is first obtained .
The observations were carried out as a part of the Beijing–Arizona–Taiwan–Connecticut ( BATC ) Multicolor Sky Survey from 1995 February to 2008 March , using 15 intermediate-band filters covering 3000–10000 Å .
Detailed comparisons show that our photometry is in agreement with previous measurements .
Based on the ages and metallicities from Caldwell et al .
and the photometric measurements here , we estimated the clusters ’ masses by comparing their multicolor photometry with stellar population synthesis models .
The results show that the sample clusters have masses between \sim 3 \times 10 ^ { 4 } M _ { \odot } and \sim 10 ^ { 7 } M _ { \odot } with the peak of \sim 4 \times 10 ^ { 5 } M _ { \odot } .
The masses here are in good agreement with those in previous studies .
Combined with the masses of young star clusters of M31 from Wang et al. , we find that the peak of mass of old clusters is ten times that of young clusters .