A modified simultaneous algebraic reconstruction technique(MSART) is presented,which takes into account both the density of pixel and the ray length across it in the error distribution.MSART can solve the edge distortion of SART effectively and makes an encouraging improvement in reconstructed image quality with sparse data.Even in the reconstruction of fewer views from limited range,good images can be obtained by choosing proper views.That is to say,the maximum error can be less than 5 % and the average error can be less than 1 %.