Abstract: In order to improve studies and application of concrete with light-burned magnesium oxide（MgO concrete）, the effect of aggregates with particle size larger than 40 mm on the autogenic volume deformation of both standard and non-standard size specimen of MgO concrete of the age as long as 1 400 days is analysed in this paper. The analysis results show that the autogenic volume deformation of the concrete specimen which has been wet-screened is larger than the specimen without wet-screening no matter how long the age is, and the increment of the autogenic volume deformation of the wet-screened non-standard specimen is smaller than that of the standard specimen（the increment of the standard specimen is about 15×10-6 while that of the non-standard specimen is about 12×10-6）; and the differences of the autogenic volume deformation of the specimen whether wet-screened or not are relatively stable and the fluctuating value with age is small, and is especially tiny when the age is beyond 3 years no matter the specimens size is of the standard or not.