In this paper, we propose a BLAST detection based on soft-decision interference cancellation for coded spatially layered multiple-input multiple-output (MIMO) systems. The proposed BLAST detection for coded MIMO systems offers a good trade-off between diversity enhancement and error propagation problem due to the interference cancellation because it uses soft-decision symbol, or symbol mean, for successive interference cancellation, instead of hard-decision symbol. In the proposed system, we apply weighted demapping concept for loglikelihood ration (LLR) calculation. In the demapping process, the signal to interference plus noise power ratio (SINR) of each stream at the detector output is easily calculated as giving weight to SINR of minimum mean-square error (MMSE) detection without calculation of post detection interference occurred in successive interference cancellation. The proposed algorithms are veried by computer simulations.