We modified the scenario analysis with a diagonal model to present a new margining system called Beta-Simulation to calculate margin requirements for portfolios that include stock index futures contract, stocks and stock options. The new system will use the estimated Beta to simplify the appropriate collateral requirement offset estimate for inter-commodity spread, thus easier than SPAN in computational procedure but offering sounder theoretical basis than TIMS for credit offset estimates among individual stock options. When testing with a portfolio consisting stocks, index futures, index options and stock options, the new margining system provides almost the same market risk protection as the SPAN system but with collateral levels that are significantly less than the level required by SPAN. All other competing systems including TIMS, Monte-Carlo simulation, and delta-gamma normal systems could not pass the likelihood-ratio test and could not provide the same coverage.